Answer:
6 is a factor of n
Step-by-step explanation:
2 is a factor of n and 3 is a factor of n means
n = 2×3×k
= 6×k
then n = 6×k
then 6 is a factor of n
Final answer:
If both 2 and 3 are factors of a number n, then 6 must also be a factor of n, because the product of unique prime factors is always a factor of that number.
Explanation:
The product of unique prime factors of a number will be a factor of that number. Since 2 and 3 are prime factors and both are factors of n, their product (which is 6) must also be a factor of n.
For example, consider the number 12. 12 is divisible by 2 and 12 is divisible by 3, and indeed, 12 is divisible by 6 as well. This holds true for any number n that has 2 and 3 as factors. Thus, we can conclude that 6 is a factor of n if both 2 and 3 are factors of n.
If the scores per round of golfers on the PGA tour are approximately normally distributed with mean 68.2 and standard deviation 2.91, what is the probability that a randomly chosen golfer's score is above 70 strokes
Answer:
26.76% probability that a randomly chosen golfer's score is above 70 strokes.
Step-by-step explanation:
Problems of normally distributed samples can be solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
In this problem, we have that:
[tex]\mu = 68.2, \sigma = 2.91[/tex]
What is the probability that a randomly chosen golfer's score is above 70 strokes?
This is 1 subtracted by the pvalue of Z when X = 70. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{70 - 68.2}{2.91}[/tex]
[tex]Z = 0.62[/tex]
[tex]Z = 0.62[/tex] has a pvalue of 0.7324.
So there is a 1-0.7324 = 0.2676 = 26.76% probability that a randomly chosen golfer's score is above 70 strokes.
Final answer:
To find the probability that a golfer's score is above 70, calculate the Z-score using the formula Z = (X - μ) / σ, where X is 70, the mean (μ) is 68.2, and the standard deviation (σ) is 2.91. The result, approximately 0.62, corresponds to a cumulative probability that must be subtracted from 1 to find the probability of scoring above 70. This process estimates there's about a 26.8% chance a golfer scores above 70.
Explanation:
The question asks about the probability that a randomly chosen golfer on the PGA tour has a score above 70 strokes, given that the scores are normally distributed with a mean of 68.2 and a standard deviation of 2.91. To find this probability, we use the Z-score formula, which is Z = (X - μ) / σ, where X is the score of interest, μ (mu) is the mean, and σ (sigma) is the standard deviation.
Calculating the Z-score for a score of 70:
Z = (70 - 68.2) / 2.91 ≈ 0.62.
Next, we consult a Z-table or use a calculator to find the probability corresponding to a Z-score of 0.62, which tells us the probability of a score being less than 70. To find the probability of a score being above 70, we subtract this value from 1.
Note: Specific values from the Z-table or calculator are not provided here. Generally, the process would involve looking up the cumulative probability for a Z-score of 0.62, which might be around 0.732. Therefore, the probability of a score above 70 would be 1 - 0.732 = 0.268. This means there's approximately a 26.8% chance that a randomly chosen golfer's score is above 70.
Karen claps her hand and hears the echo from a distant wall 0.113 s later. How far away is the wall? The speed of sound in air is 343 m/s
Answer:
19.3795 m
Step-by-step explanation:
If sound travels at 343 m/s and it took Karen 0.113 s to hear the echo from the wall, the distance travelled by the sound is:
[tex]D=343\frac{m}{s} *0.113\ s\\D= 38.759\ m[/tex]
Note that the distance calculated above is the distance travelled from Karen to the wall and then back from the wall to Karen. Therefore, the distance between Karen and the wall is:
[tex]d=\frac{38.759}{2}\\d=19.3795\ m[/tex]
The wall is 19.3795 m away from Karen.
The wall is 19.39 meters away.
To find the distance to the wall based on the echo, we use the speed of sound and the time it takes for the echo to return. The time given includes both the journey to the wall and back, so we need to divide it by 2.
1. Time for sound to travel to the wall and back: 0.113 s
2. Time for sound to travel one way:
0.113 s / 2 = 0.0565 s
3. Speed of sound: 343 m/s
4. Distance = Speed x Time
343 m/s * 0.0565 s = 19.39
Therefore, the wall is 19.39 meters away from Karen.
43. A one sample test for a proportion is being performed. If the critical value is 2.33 and the test statistics is 1.37, a) The null hypothesis should not be rejected. b) The alternative hypothesis cannot be rejected. c) The null hypothesis should be rejected. d) The sample size should be decreased.
Answer:
Option A) The null hypothesis should not be rejected.
Step-by-step explanation:
We are given the following in the question:
A one sample test for a proportion is being performed.
Critical Value = 2.33
Test statistic = 1.37
Since the critical value is positive and the calculated test statistic is positive, thus it is a right tailed test for a proportion.
The null and alternate hypothesis can be written as:
[tex]H_{0}: p \leq p_0\\H_A: p > p_0[/tex]
Since the calculated test statistic is less than the critical value, we fail to reject the null hypothesis.
We accept the null hypothesis.
Thus, the correct answer is
Option A) The null hypothesis should not be rejected.
Classify the following data. Indicate whether the data is qualitative or quantitative, indicate whether the data is discrete, continuous, or neither, and indicate the level of measurement for the data.The number of days traveled last month by 100100 randomly selected employees.Are these data qualitative or quantitative? O A. Qualitative B. Quantitative Are these data discrete or continuous? A. Discrete B. Continuous C. Neither What is the highest level of measurement the data possesses? A. Nominal B. Ordinal C. Interval D. Ratio
The data, the number of days traveled by randomly selected employees, is classified as quantitative, discrete data with a ratio level of measurement.
Explanation:
The data in question, namely, the number of days traveled last month by 100100 randomly selected employees, is considered quantitative data. This is because it deals with numbers that can be quantitatively analyzed. In terms of whether the data is discrete or continuous, it is discrete. The number of days traveled can be counted in whole numbers (you can't travel 2.5 days for example); thus, it is a countable set of data. Lastly, considering the level of measurement, the data falls under the ratio level as it not only makes sense to say that someone traveled more days than someone else (therefore an ordered relationship), but it also makes sense to say someone traveled twice as many days as someone else (giving us a proportion and a well-defined zero point).
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(b) For one each of your concrete and your hypothetical populations, give an example of a probability question and an example of an inferential statistics question.
Hi, you haven't provided the concrete and hypothetical populations, I'll be using people with red hair in Texas as our population, but you can use a similar approach for the population you decide to use.
Answer:
Probability question: For a known group of people in Texas, what is the probability that we select two people with red hair? Inferential statistics question: From a large population, selected randomly, we found that five of them have red hair, what is the total proportion of people with red hair in Texas?Explanation:
As you can see from the questions, the main difference between statics and probability has to do with knowledge, what do we know about our population? For the first question (probability) we talked about a known group of people, and base on our knowledge we ask about the probability of selecting people with red hair. For the second question (statistics) we are asked to make an inference about all the population based just on a sample (we don't have all the knowledge), also we say that the last question is Inferential because the data come from a large population selected randomly.
Final answer:
An example of a probability question could involve finding the likelihood of a statistics student using a product weekly based on a survey sample. Meanwhile, an inferential statistics question might use a t-test to infer differences in protein value between two lots of hay.
Explanation:
In the context of probability and inferential statistics, an example of a probability question for a concrete population might be: "If a random sample of 25 statistics students was surveyed, and six reported using a certain product within the past week, what is the probability that any given statistics student uses the product weekly?"
An example of an inferential statistics question using hypothetical population data could be: "Using a t-test to compare the mean protein value of two lots of alfalfa hay, can we infer that there is a significant difference between their protein contents?" The t-test determines if the observed difference in means is likely due to chance or if it is statistically significant.
These examples illustrate how probability is used to model uncertainty and random events, while inferential statistics are employed to make educated guesses about a population from sample data, such as calculating a confidence interval or testing a hypothesis.
One angle is twice its supplement increased by 102 degrees. Find the measures of the two supplementary angles.
One angle and its supplement give 180 when summed:
[tex]\alpha+\beta = 180[/tex]
This implies that
[tex]\alpha = 180-\beta[/tex]
we also know that
[tex]\alpha = 2\beta+102[/tex]
So, we wrote [tex]\alpha[/tex] as [tex]180-\beta[/tex], but also as [tex]2\beta+102[/tex]. So, the two expressions must equal each other, because they both equal [tex]\alpha[/tex]:
[tex]180-\beta = 2\beta+102 \iff 78=3\beta \iff \beta = 26[/tex]
This implies that [tex]\alpha[/tex] must complete [tex]\beta[/tex] so that they reach 180 together:
[tex]\alpha = 180-\beta = 180-26 = 154[/tex]
The concept of supplementary angles is used to solve the given problem. By forming a pair of linear equations from the problem and solving them, the measures of the two angles are found to be 154 degrees and 26 degrees respectively.
Explanation:
The subject in question here involves the concept of supplementary angles. Supplementary angles are two angles that add up to 180 degrees. In this case, the problem states that one angle is twice its supplement increased by 102 degrees. This forms a pair of linear equations that we can solve for.
Let's denote the unknown angle as x and its supplement as y. According to the problem, we have the following system of equations:
x + y = 180 (since they are supplementary)x = 2y + 102 (according to the problem description)By substitifying the second equation into the first, we receive: 2y + 102 + y = 180. Solving this equation gives y = 26 degrees. Substituting y back into the first equation gives x = 180 - 26 = 154 degrees.
So the two supplementary angles are 154 degrees and 26 degrees.
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When running a half marathon (13.1 miles), it took Grant 7 minutes and 45 seconds to run from mile marker 1 to mile marker 2, and 19 minutes and 15 seconds to run from mile marker 2 to mile marker 4.
A) As Grant's distance from the starting line increased from 1 to 4 miles, what average speed (in miles per minute) did he run?
B) 69 minutes after starting the race Grant passed mile marker 9. What average speed in miles per minute will Grant need to run, from mile marker 9 to the end of the race, to meet his goal to complete the 13.1 mile half-marathon in 110 minutes?
Answer:
Step-by-step explanation:
The length of the half marathon is 13.1 miles. it took Grant 7 minutes and 45 seconds to run from mile marker 1 to mile marker 2. Converting 7 minutes and 45 seconds to minutes, it becomes
7 + 45/60 =7.75 minutes
Speed = distance/time
Therefore, his speed from mile marker 1 to mile marker 2 is
1/7.75 = 0.129 miles per minute
He spent 19 minutes and 15 seconds to run from mile marker 2 to mile marker 4. Converting 19 minutes and 15 seconds to minutes, it becomes
19 + 15/60 =19.25 minutes
Therefore, his speed from mile marker 2 to mile marker 4 is
2/19.255 = 0.104 miles per minute
A) his average speed from miles 1 to 4 would be
(0.129 + 0.104)/2 = 0.1165 miles per minute.
B) after running the 9th mile, distance remaining would be
13.1 - 9 = 4.1 miles
Time left to complete the race would be
110 - 69 = 41 minutes
Average speed needed to complete the race would be
4.1/41 = 0.1 miles per minute.
Final answer:
Grant's average speed from mile 1 to mile 4 was approximately 0.1481 miles per minute. To complete the half marathon in his goal time, he needs to run the last 4.1 miles at an average speed of approximately 0.1 miles per minute.
Explanation:
We're given that Grant took 7 minutes and 45 seconds to run from mile marker 1 to mile marker 2, and 19 minutes and 15 seconds to run from mile marker 2 to mile marker 4. To find Grant's average speed from mile marker 1 to mile marker 4, we first convert the time into minutes. He ran 2 miles in 7.75 minutes and then 2 miles in 19.25 minutes. That's a total of 4 miles in 7.75 + 19.25 = 27 minutes, resulting in an average speed of 4 miles / 27 minutes ≈ 0.1481 miles per minute.
Then, we find out how fast Grant needs to run to complete the half marathon in 110 minutes. Grant is at mile marker 9 after 69 minutes, leaving him with 110 - 69 = 41 minutes to complete the remaining 13.1 - 9 = 4.1 miles. The average speed required for this last stretch is 4.1 miles / 41 minutes ≈ 0.1 miles per minute.
Choose the accurate description of why it is not correct to make a pie chart for the social usage hours or the entertainment usage hours.
Answer:
The question is incomplete or missing some part, but I have answered it appropriately.
Step-by-step explanation:
The question is incomplete, but I will give a detailed description of where pie chart are appropriate to use. A pie chart as we known is a divided circle containing breakdown d and this are developed into a table from calculations and then a chart is developed. The circle in a pie chart are divided into sectors where the angle of each sector is directly proportional to the frequency of the item or data that is being represented.
The process is done by finding the sum of all the frequencies, the sum is then used to divide 360 degree which is the total degree in a complete circle. thereafter each of the frequencies is used to multiply this result to arrive at the sectoral angle for each item. for example, the breakdown of weekkly expenditures of a house wife. the expensiture are marked with the amount spent on each. this information can be represented or illustrated on pie chart.
It should be noted that a pie chart is only suitable for a single set of data and not more than one date as is the case of histogram where more than one grouped or un-grouped data maybe represented or ilustrated on a histogram. if this is the case, pie chart are best employed when making a description between a single part of a data and not the whole set.
An engineer is comparing voltages for two types of batteries (K and Q) using a sample of 68 type K batteries and a sample of 84 type Q batteries. The mean voltage is measured as 8.98 for the type K batteries with a standard deviation of 0.791, and the mean voltage is 9.20 for type Q batteries with a standard deviation of 0.455. Conduct a hypothesis test for the conjecture that the mean voltage for these two types of batteries is different. Let μ1 be the true mean voltage for type K batteries and μ2 be the true mean voltage for type Q batteries. Use a 0.02 level of significance.
a. Step 1 of 4: State the null and alternative hypotheses for the test.b. Step 2 of 4: Compute the value of the test statistic. Round your answer to two decimal places.c. Step 3 of 4: Determine the decision rule for rejecting the null hypothesis H0. Round the numerical portion of your answer to two decimal places.d. Step 4 of 4: Make the decision for the hypothesis test.
Answer:
Step-by-step explanation:
Show that the given set of functions is orthogonal with respect to the given weight on the prescribed interval. Find the norm of each function in the set.
Answer/Explanation
The complete question is:
Show that the set function {1, cos x, cos 2x, . . .} is orthogonal with respect to given weight on the prescribed interval [- π, π]
Step-by-step explanation:
If we make the identification For ∅° (x) = 1 and ∅n(x) = cos nx, we must show that ∫ lim(π) lim(-π) .∅°(x)dx = 0 , n ≠0, and ∫ lim(π) lim(-π) .∅°(x)dx = 0, m≠n.
Therefore, in the first case, we have
(∅(x), ∅(n)) ∫ lim(π) lim(-π) .∅°(x)dx = ∫ lim(π) lim(-π) cosn(x)dx
This will therefore be equal to :
1/n sin nx lim(π) lim(-π) = 1/n [sin nπ - sin(-nπ)] = 0 , n ≠0 (In the first case)
and in the second case, we have,,
(∅(m) , ∅(n)) = ∫ lim(π) lim(-π) .∅°(x)dx
This will therefore be equal to:
∫ lim(π) lim(-π) cos mx cos nx dx
Therefore, 1/2 ∫ lim(π) lim(-π)( cos (m+n)x + cos( m-n)x dx (Where this equation represents the trigonometric function)
1/2 [ sin (m+n)x / m+n) ]+ [ sin (m-n)x / m-n) ] lim(π) lim(-π) = 0, m ≠ n
Now, to go ahead to find the norms in the given set intervals, we have,
for ∅°(x) = 1 we have:
//∅°(x)//² = ∫lim(π) lim(-π) dx = 2π
So therefore, //∅°(x)//² = √2π
For ∅°∨n(x) = cos nx , n > 0.
It then follows that,
//∅°(x)//² = ∫lim(π) lim(-π) cos²nxdx = 1/2 ∫lim(π) lim(-π) [1 + cos2nx]dx = π
Thus, for n > 0 , //∅°(x)// = √π
It is therefore ggod to note that,
Any orthogonal set of non zero functions {∅∨n(x)}, n = 0, 1, 2, . . . can be normalized—that is, made into an orthonormal set by dividing each function by its norm. It follows from the above equations that has been set.
Therefore,
{ 1/√2π , cosx/√π , cos2x/√π...} is orthonormal on the interval {-π, π}.
According to Newton's law of cooling, if an object at temperature T is immersed in a medium having the constant temperature M, then the rate of change of T is proportional to the difference of temperature M-T. This gives the differential equation dT/dt=k(M-T)Solve the differential equation for T.
Answer:
[tex] T(t) = M -C_1 e^{-kt}[/tex]
And as we can see that represent the solution for the differential equation on this case.
Step-by-step explanation:
For this case we have the following differential equation:
[tex] \frac{dT}{dt}= k(M-T)[/tex]
We can rewrite this expression like this:
[tex] \frac{dT}{M-T} = k dt[/tex]
We can us the following susbtitution for the left part [tex] u = M-T[/tex] then [tex] du= -dt[/tex] and if we replace this we got:
[tex] \frac{-du}{u} = kdt[/tex]
We can multiply both sides by -1 and we got;
[tex] \frac{du}{u} =-k dt[/tex]
Now we can integrate both sides and we got:
[tex] ln |u| = -kt + C[/tex]
Where C is a contant. Now we can exponetiate both sides and we got:
[tex] u(t) =e^{-kt} *e^C = C_1 e^{-kt}[/tex]
Where [tex] C_1 = e^C[/tex] is a constant. And now we can replace u and we got this:
[tex] M-T = C_1 e^{-kt}[/tex]
And if we solve for T we got:
[tex] T(t) = M -C_1 e^{-kt}[/tex]
And as we can see that represent the solution for the differential equation on this case.
The solution to the differential equation representing Newton's law of cooling is calculated by rearranging the equation and then integrating both sides. The general solution for the temperature of an object over time is given by T = M - Ce^-kt where M is the ambient temperature, T is the temperature of the object, C is a constant, and k is the constant of proportionality.
Explanation:To solve the given differential equation which represents Newton's law of cooling, we shall proceed with integrating both sides. This is in the form of a separable first order differential equation and can be written in the form as follows:
dT / (M - T) = k dt
By re-arranging and integrating both sides, we can find the solution. When we integrate both sides, we get:
- ln |M - T| = kt + C
Where C is the constant of integration. Simplifying further:
T = M - Ce-kt
This is the general solution to the temperature T of an object over time t according to Newton's law of cooling.
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Taxi Fares are normally distributed with a mean fare of $22.27 and a standard deviation of $2.20.
(A) Which should have the greater probability of falling between $21 & $24;
the mean of a random sample of 10 taxi fares or the amount of a single random taxi fare? Why?
(B) Which should have a greater probability of being over $24-the mean of 10 randomly selected taxi fares or the amount of a single randomly selected taxi fare? Why?
A single taxi fare is more likely to fall between $21 & $24 or be over $24 compared to the mean of a sample of 10 taxi fares.
The question revolves around understanding the distribution of taxi fares and comparing the probabilities associated with the means of samples versus individual observations from a normally distributed population.
(A) Probability of falling between $21 & $24
A single taxi fare has greater variability and thus a greater probability of falling within the range of $21 & $24 compared to the mean of a random sample of 10 taxi fares. This is due to the Central Limit Theorem, which states that the distribution of the sample means will have a smaller standard deviation than that of individual observations, also known as the standard error. For a sample size of 10, the standard error is the population standard deviation divided by the square root of the sample size, which leads to a narrower distribution for the sample means compared to the distribution of individual fares.
(B) Probability of being over $24
The probability of a single randomly selected taxi fare being over $24 is greater than that of the mean of 10 randomly selected taxi fares. This is because individual observations are more spread out, as indicated by the standard deviation of the population, whereas the distribution of sample means is more concentrated around the mean due to the reduced standard error.
(A) The mean of a random sample of 10 taxi fares should have the greater probability of falling between $21 and $24.
(B) The amount of a single randomly selected taxi fare should have a greater probability of being over $24.
The Central Limit Theorem states that the distribution of the sample means will approach a normal distribution as the sample size increases, with the mean of the sample means being equal to the population mean and the standard deviation of the sample means (also known as the standard error) being equal to the population standard deviation divided by the square root of the sample size.
For a single taxi fare, the probability of falling between $21 and $24 can be calculated using the standard normal distribution. We first find the Z-scores corresponding to $21 and $24:
Z-score for $21: [tex]\( Z = \frac{X - \mu}{\sigma} = \frac{21 - 22.27}{2.20} = -0.58 \)[/tex]
Z-score for $24: [tex]\( Z = \frac{X - \mu}{\sigma} = \frac{24 - 22.27}{2.20} = 0.80 \)[/tex]
Using a standard normal table or calculator, we can find the probabilities corresponding to these Z-scores:
P(-0.58 < Z < 0.80) = P(Z < 0.80) - P(Z < -0.58) ≈ 0.788 - 0.278 ≈ 0.510
For the mean of a random sample of 10 taxi fares, the standard error (SE) is:
[tex]\( SE = \frac{\sigma}{\sqrt{n}} = \frac{2.20}{\sqrt{10}} \approx 0.70 \)[/tex]
Now we calculate the Z-scores for $21 and $24 using the standard error:
[tex]Z-score for $21: \( Z = \frac{\bar{X} - \mu}{\sigma/\sqrt{n}} = \frac{21 - 22.27}{0.70} \approx -1.75 \)[/tex]
[tex]Z-score for $24: \( Z = \frac{\bar{X} - \mu}{\sigma/\sqrt{n}} = \frac{24 - 22.27}{0.70} \approx 2.53 \)[/tex]
The probability that the sample mean falls between $21 and $24 is then:
P(-1.75 < Z < 2.53) = P(Z < 2.53) - P(Z < -1.75) ≈ 0.994 - 0.040 ≈ 0.954
Comparing the two probabilities, 0.954 for the sample mean is greater than 0.510 for a single fare.
Explanation for (B):
For a single taxi fare, we already calculated the Z-score for $24, which is 0.80. The probability of a single fare being over $24 is:
P(Z > 0.80) = 1 - P(Z < 0.80) ≈ 1 - 0.788 ≈ 0.212
For the mean of a random sample of 10 taxi fares, we calculated the Z-score for $24 as 2.53. The probability of the sample mean being over $24 is:
P(Z > 2.53) = 1 - P(Z < 2.53) ≈ 1 - 0.994 ≈ 0.006
Comparing the two probabilities, 0.212 for a single fare is greater than 0.006 for the sample mean. Therefore, the amount of a single randomly selected taxi fare has a greater probability of being over $24.
Let (X1, X2, X3, X4) be Multinomial(n, 4, 1/6, 1/3, 1/8, 3/8). Derive the joint mass function of the pair (X3, X4). You should be able to do this with almost no computation.
Answer:
The random variables in this case are discrete since they have a Multinomial distribution.
The probability mass function for a discrete random variable X is given by:
[tex]P(X=x_{i} )[/tex]
Where are [tex]x_{i}[/tex] are possible values of X.
The joint probability mass function of two discrete random variables X and Y is defined as
P(x,y) =P(X=x,Y=y).
It follows that, The joint probability mass function of [tex]X_{3} , X_{4}[/tex] is :
[tex]P(X_{3}, X_{4} ) = P( X_{3} = x_{3}, X_{4} = x_{4} ) =\frac{1}{8} +\frac{3}{8} =\frac{1}{2}[/tex]
In a Multinomial Distribution, variables are independent. Hence, the joint mass function of a pair (X3 , X4) is the product of their individual mass functions. Their specific joint mass function equals P(X3=x3)P(X4=x4) = (n choose x3)(1/8)^x3(3/8)^x4 for x3+x4 ≤ n and x3, x4 ≥ 0.
Explanation:This problem relates to the concept of a Multinomial Distribution in probability theory. The Multinomial Distribution describes the probabilities of potential outcomes from a multinomial experiment.
In this particular case, you are given that (X1, X2, X3, X4) follows a Multinomial Distribution with parameters n (number of trials) and 4 categories, with known probabilities 1/6, 1/3, 1/8, and 3/8 respectively.
You are asked to derive the joint mass function of the pair (X3, X4). This is actually very straightforward. Due to the properties of a multinomial distribution, these two variables are independent and the joint mass function is simply the product of the individual mass functions.
So the joint mass function of X3 and X4 would be P(X3=x3, X4=x4) = P(X3=x3)P(X4=x4) = (n choose x3)(1/8)^x3(3/8)^x4 provided x3+x4 ≤ n and each of x3,x4 are nonnegative.
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Suppose a student carrying a flu virus returns to an isolated college campus of 2000 students. Determine a differential equation governing the number of students x(t) who have contracted the flu if the rate at which the disease spreads is proportional to the number of interactions between students with the flu and students who have not yet contracted it. (Use k > 0 for the constant of proportionality and x for x(t).)
Final answer:
The differential equation governing the spread of flu among students on a college campus is modeled by the logistic equation dx/dt = kx(2000 - x), assuming a constant rate of interactions and no outside influences.
Explanation:
The differential equation governing the number of students x(t) who have contracted the flu on an isolated college campus, where the rate of disease spread is proportional to the number of interactions between infected and susceptible students, can be modeled using principles of epidemiology. The total number of students is 2000, and if we use k for the constant of proportionality, we can denote the number of susceptible students as 2000 - x, because x represents the number of infected students. Hence, the rate of change of x, given by dx/dt, is proportional to the product of the number of students who have the flu and the number who do not, which is kx(2000-x). The differential equation is thus:
dx/dt = kx(2000 - x)
This is a standard form of the logistic differential equation, often used in the SIR model in epidemiology to describe how a disease spreads in a population.
We tend to think of light surrounding us, like air. But light travels, always.
Bill is standing 2 meters from his mirror.
Approximately how many seconds will it take a pulse of light to bounce off his forehead, hit the mirror, and return back to his eye?
Answer:
1.33 x 10⁻⁸ seconds
Step-by-step explanation:
Assuming that the speed of light is 299,792,458 m/s, and that in order to bounce of Bill's forehead, hit the mirror and return back to his eyes, light must travel 4 meters (distance to the mirror and back) the time that it takes for light to travel is:
[tex]t=\frac{4}{299,792,458} \\t=1.33*10^{-8}[/tex]
It takes 1.33 x 10⁻⁸ seconds.
Evaluate the triple integral ∭Tx2dV, where T is the solid tetrahedron with vertices (0,0,0), (3,0,0), (0,3,0), and (0,0,3).
To evaluate the triple integral ∭Tx²dV, we need to integrate over the solid tetrahedron T defined by the vertices (0,0,0), (3,0,0), (0,3,0), and (0,0,3).
Explanation:To evaluate the triple integral ∭Tx²dV, we need to integrate over the solid tetrahedron T defined by the vertices (0,0,0), (3,0,0), (0,3,0), and (0,0,3). Since T is a three-dimensional shape, we need to perform a triple integral.
The limits of integration for each variable are as follows:
x: 0 to 3-y-z
y: 0 to 3-z
z: 0 to 3
Substituting the limits into the integrand Tx², we can then evaluate the triple integral by integrating with respect to x, y, and z in the given limits.
This type of sampling makes use of geographical blocks or voting districts as a sampling frame in order to cut down a huge population size.
Group of answer choices
a. Cluster
b. Systematic
c. Stratified
d. Simple
Answer:
The correct option is a) Cluster.
Step-by-step explanation:
Consider the provided information.
Types of sampling:
Systematic sampling: list of elements is counted off.Simple random sample: It is a subset of the population chosen from a larger set. Cluster sampling: It divides the population into groups, usually geographically.Stratified sampling: It divide population into groups called strata. but this time population might be separated into males and femalesHere, the population is divided into geographical blocks,
Thus, the type of sampling is cluster.
Therefore the correct option is a) Cluster.
The lives of certain extra-life light bulbs are normally distributed with a mean equal to 1350 hours and a standard deviation equal to 18 hours1. What percentage of bulbs will have a life between 1350 and 1377 hr?2. What percentage of bulbs will have a life between 1341 and 1350 hr?3. What percentage of bulbs will have a life between 1338 and 1365 hr?4. What percentage of bulbs will have a life between 1365 and 1377 hr?
In order to find the percentage of bulbs with a certain lifespan, one must calculate the z-scores for the given values and find the probabilities using the standard normal distribution, converting these into percentages.
Explanation:The student's question involves using the properties of the normal distribution to determine the probability of light bulb life spans within certain intervals. To solve these problems, the z-score formula is used, which is (X - μ) / σ, where X is the value of interest, μ is the mean, and σ is the standard deviation.
To find the percentage of bulbs that will have a life between 1350 and 1377 hours, you calculate the z-score for both values and use a standard normal distribution table or calculator to find the area between these z-scores.For the percentage of bulbs that will have a life between 1341 and 1350 hours, follow the same process as above, using the respective values for the z-score computation.Repeat the procedure for the other intervals, 1338 to 1365 hours, and 1365 to 1377 hours, to determine the desired probabilities.Remember that the answer will be in the form of a percentage representing the likelihood that any given bulb falls within the specified hour range.
Find the complete time-domain solution y(t) for the rational algebraic output transform Y(s):_________
Answer:
y(t)= 11/3 e^(-t) - 5/2 e^(-2t) -1/6 e^(-4t)
Step-by-step explanation:
[tex] Y(s)=\frac{s+3}{(s^2+3s+2)(s+4)} + \frac{s+3}{s^2+3s+2} +\frac{1}{s^2+3s+2} [/tex]
We know that [tex] s^2+3s+2=(s+1)(s+2)[/tex], so we have
[tex] Y(s)=\frac{s+3+(s+3)(s+4)+s+4}{(s+1)(s+2)(s+4)} [/tex]
By using the method of partial fraction we have:
[tex] Y(s)=\frac{11}{3(s+1)} - \frac{5}{2(s+2)} -\frac{1}{6(s+4)} [/tex]
Now we have:
[tex] y(t)=L^{-1}[Y(s)](t) [/tex]
Using linearity of inverse transform we get:
[tex] y(t)=L^{-1}[\frac{11}{3(s+1)}](t) -L^{-1}[\frac{5}{2(s+2)}](t) -L^{-1}[\frac{1}{6(s+4)}](t) [/tex]
Using the inverse transforms
[tex] L^{-1}[c\frac{1}{s-a}]=ce^{at} [/tex]
we have:
[tex] y(t)=11/3 e^{-t} - 5/2 e^{-2t} -1/6 e^(-4t) [/tex]
Following are the published weights (in pounds) of all of the team members of Football Team A from a previous year.178; 203; 212; 212; 232; 205; 185; 185; 178; 210; 206; 212; 184; 174;185; 242; 188; 212; 215; 247; 241; 223; 220; 260; 245; 259; 278; 270;280; 295; 275; 285; 290; 272; 273; 280; 285; 286; 200; 215; 185; 230;250; 241; 190; 260; 250; 302; 265; 290; 276; 228; 265Organize the data from smallest to largest value.Part (a)Find the median.Part (b)Find the first quartile. (Round your answer to one decimal place.)Part (c)Find the third quartile. (Round your answer to one decimal place.)Part (d)The middle 50% of the weights are from to .Part (e)If our population were all professional football players, would the above data be a sample of weights or the population of weights? Why? (choose one)-The above data would be a sample of weights because they represent a subset of the population of all football players.-The above data would be a sample of weights because they represent all of the players from one year. -The above data would be a population of weights because they represent all of the football players.-The above data would be a population of weights because they represent all of the players on a team.Part (f)If our population were Football Team A, would the above data be a sample of weights or the population of weights? Why? (choose one)-The data would be a sample of weights because they represent all of the professional football players.-The data would be a population of weights because they represent all of the players on Football Team A. - The data would be a sample of weights because they represent all of the players on Football Team A.-The data would be a population of weights because they represent all of the professional football players.Part (g)Assume the population was Football Team A. Find the following. (Round your answers to two decimal places.)(i) the population mean, ? ______(ii) the population standard deviation, ? _____(iii) the weight that is 3 standard deviations below the mean ____(iv) When Player A played football, he weighed 229 pounds. How many standard deviations above or below the mean was he? _____standard deviations _______ (above or below) the meanPart (h)That same year, the average weight for Football Team B was 240.08 pounds with a standard deviation of 44.38 pounds. Player B weighed in at 209 pounds. Suppose Player A from Football Team A weighed 229 pounds. With respect to his team, who was lighter, Player B or Player A? How did you determine your answer? (choose one)-Player A, because he is more standard deviations away from his team's mean weight.-Player B, because he is more standard deviations away from his team's mean weight. -Player A, because Football Team A has a higher mean weight.-Player B, because Football Team B has a higher mean weight.Expert Answer
Answer:
a. 241; b. 206.0; c. 272.0; d. 174 to 232; other answers (see below).
Step-by-step explanation:
First, at all, we need to organize the data from the smallest to the largest value:
174 178 178 184 185 185 185 185 188 190 200 203 205 206 210 212 212 212 212 215 215 220 223 228 230 232 241 241 242 245 247 250 250 259 260 260 265 265 270 272 273 275 276 278 280 280 285 285 286 290 290 295 302
This step is important to find the median, the first quartile, and the third quartile. There are numerous methods to find the median and the other quartiles, but in this case, we are going to use a method described by Tukey, and it does not need calculators or software to estimate it.
Part a: MedianIn this case, we have 53 values (an odd number of values), the median is the value that has the same number of values below and above it, so what is the value that has 26 values below and above it? Well, in the organized data above this value is the 27th value, because it has 26 values above and below it:
174 178 178 184 185 185 185 185 188 190 200 203 205 206 210 212 212 212 212 215 215 220 223 228 230 232 241 241 242 245 247 250 250 259 260 260 265 265 270 272 273 275 276 278 280 280 285 285 286 290 290 295 302
The median is 241.
Part b: First QuartileFor the first quartile, we need to calculate the median for the lower half of the values from the median previously obtained. Since we have an odd number of values (53), we have to include the median in this calculation. We have 27 values (including the median), so the "median" for these values is the value with 13 values below and above it.
174 178 178 184 185 185 185 185 188 190 200 203 205 206 210 212 212 212 212 215 215 220 223 228 230 232 241
Since we are asking to round the answer to one decimal place, the first quartile is 206.0
Part c: Third QuartileWe use the same procedure used to find the first quartile, but in this case, using the upper half of the values.
241 241 242 245 247 250 250 259 260 260 265 265 270 272 273 275 276 278 280 280 285 285 286 290 290 295 302
So, the third quartile is 272.0
Part d: The middle 50%The second quartile is the median and "50% of the data lies below this point" (Quartile (2020), in Wikipedia). Having this information into account, 50% of the weights lies below the median 241.
Thus, the middle 50% of the weights are from 174 to 232.
174 178 178 184 185 185 185 185 188 190 200 203 205 206 210 212 212 212 212 215 215 220 223 228 230 232 241
Part e: Sample or Population 1If the population were all professional football players, the right option is:
The above data would be a sample of weights because they represent a subset of the population of all football players.
It represents a sample. Supposing Football Team A are all professional, they can be considered a sample from all professional football players.
Part f: Sample or Population 2If the population were Football Team A, the right option is:
The data would be a population of weights because they represent all of the players on Football Team A.
Part g: population mean and morePart iThe mean for the population of weights of Football Team A is the sum of all weights (12529 pounds) divided by the number of cases (53).
[tex] \\ \mu = \frac{12529}{53} = 236.39622641509433 [/tex]
[tex] \\ \mu = \frac{12529}{53} = 236.40 [/tex]
Part iiThe standard deviation for the population is:
[tex] \\ \sigma = \sqrt(\frac{(x_{1}-\mu)^2 + (x_{2}-\mu)^2 + ... + (x_{n}-\mu)^2}{n}) [/tex]
In words, we need to take either value, subtract it from the population mean, square the resulting value, sum all the values for the 53 cases (in this case, the value is 74332.67924), divide the value by 53 (1402.50338) and take the square root of it (37.45001).
Then, the population standard deviation is 37.45.
Part iiiThe weight that is 3 standard deviations below the mean can be obtained using the following formula:
[tex] \\ z = \frac{x - \mu}{\sigma} [/tex]
[tex] \\ \mu= 236.40\;and\;\sigma=37.45[/tex]
Then, in the case of three standard deviations below the mean, z = -3.
[tex] \\ -3 = \frac{x - 236.40}{37.45} [/tex]
[tex] \\ x = -3*37.45 + 236.40 [/tex]
[tex] \\ x = 124.05 [/tex]
Part ivFor the player that weights 209 pounds:
[tex] \\ z = \frac{x - \mu}{\sigma} [/tex]
[tex] \\ z = \frac{229 - 236.40}{37.45} [/tex]
[tex] \\ z = -0.19 [/tex]
Part h: Comparing Weights of Team A and Team BFor Team B, we have a mean and a standard deviation of:
[tex] \\ \mu=240.08\;and\;\sigma=44.38[/tex]
And Player B weighed 229 pounds.
[tex] \\ z = \frac{x - \mu}{\sigma} [/tex]
[tex] \\ z = \frac{229 - 240.08}{44.38} [/tex]
[tex] \\ z = -0.70 [/tex]
This value says that Player B is lighter with respect to his team than Player A, because his weight is 0.70 below the mean of Football Team B, whereas Player A has a weight that is closer to the mean of his team. So, the answer is:
Player B, because he is more standard deviations away from his team's mean weight.
Which fraction represents this decimal? 0.1234
A.1234/10000
B.617/500
C.1/2
D.1234/9999
Answer:
B
Step-by-step explanation:
617/500 = 1234/1000
Therefore option B is the answer.
The math club at a certain school has 10 members, of which 6 are seniors and 4 juniors. In how many ways can they form a group of 5 members to go to a tournament, if at least 4 of them have to be seniors (aka either a group of 4 seniors and 1 junior, or a group of 5 seniors
Answer: 66 ways
Step-by-step explanation:
Given;
Number of senior math club members = 6
Number of junior math club members = 4
Total number of members of the club = 10
To form a group of 5 members with at least 4 seniors.
N = Na + Nb
Na = number of possible ways of selecting 4 seniors and 1 junior
Nb = number of possible ways of selecting 5 seniors.
Since the selection is does not involve ranks(order is not important)
Na = 6C4 × 4C1 = 6!/4!2! × 4!/3!1! = 15 ×4 = 60
Nb = 6C5 = 6!/5!1! = 6
N = Na + Nb = 60+6
N = 66 ways
Using the combination formula, it is found that there are 66 ways to form the groups.
The order in which the students are selected is not important, hence, the combination formula is used to solve this question.
What is the combination formula?[tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by:
[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]
In this problem, the possible groups are:
One junior from a set of 4 and 4 seniors from a set of 6.5 seniors from a set of 6.Hence:
[tex]T = C_{4,1}C_{6,4} + C_{6,5} = \frac{4!}{1!3!}\frac{6!}{4!2!} + \frac{6!}{5!1!} = 4(15) + 6 = 60 + 6 = 66[/tex]
There are 66 ways to form the groups.
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Exposure to microbial products, especially endotoxin, may have an impact on vulnerability to allergic diseases. The following are data on concentration (EU/mg) in settled dust for one sample of urban homes and another of farm homes.
U: 6.0 5.0 11.0 33.0 4.0 5.0 80.0 18.0 35.0 17.0 23.0
F: 2.0 15.0 12.0 8.0 8.0 7.0 6.0 19.0 3.0 9.8 22.0 9.6 2.0 2.0 0.5
Determine the sample mean for each sample.
Answer:
Sample mean for U=21.5
Sample mean for F=8.4
Step-by-step explanation:
[tex]Sample mean of u=xbar_{u} =\frac{sum(xi)}{n}[/tex]
Where xi are the observations in the urban homes sample and n is the number of observations in the urban homes sample
[tex]sample mean of u=xbar_{u} =\frac{6+5+11+33+4+5+80+18+35+17+23}{11}[/tex]
[tex]sample mean of u=xbar_{u} =\frac{237}{11}=21.545[/tex]
Rounding it to one decimal places
[tex]sample mean of u=xbar_{u}=21.5[/tex]
Now for second sample
[tex]Sample mean of F=xbar_{F} \frac{sumxi}{n}[/tex]
Where xi are the observations in the farm homes sample and n is the number of observations in the farm homes sample
[tex]Sample mean of F=xbar_{F} =\frac{2+15+12+8+8+7+6+19+3+9.8+22+9.6+2+2+0.5)}{15}[/tex]
[tex]Sample mean of F=xbar_{F} =\frac{125.9}{15} =8.393[/tex]
Rounding it to one decimal places
[tex]Sample mean of F=xbar_{F} =8.4[/tex]
The sample mean for urban homes (U) is 21.54 and the sample mean for farm homes (F) is 7.73.
Explanation:To find the sample mean, you sum up all the data points and then divide by the number of data points. For the Urban homes (U), we first add up all the data points: 6.0 + 5.0 + 11.0 + 33.0 + 4.0 + 5.0 + 80.0 + 18.0 + 35.0 + 17.0 + 23.0 = 237.0. The number of data points is 11, so the sample mean for U is 237.0 / 11 = 21.54 (rounded to two decimal places).
For Farm homes (F), add up all the data points: 2.0 + 15.0 + 12.0 + 8.0 + 8.0 + 7.0 + 6.0 + 19.0 + 3.0 + 9.8 + 22.0 + 9.6 + 2.0 + 2.0 + 0.5 = 115.9. The number of data points is 15, so the sample mean for F is 115.9 / 15 = 7.73 (rounded to two decimal places).
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Assume Y=1+X+u, where X, Y, and u=v+X are random variables, v is independent of X; E(v)=0, Var(v)=1, E(X)=1, and Var(X)=2.
Calculate E(u | X=1), E(Y | X=1), E(u | X=2), E(Y | X=2), E(u | X), E(Y | X), E(u) and E(Y).
Answer:
a) [tex] E(u|X=1)= E(v|X=1) + E(X|X=1) = E(v) +1 = 0 +1 =1+[/tex]
b) [tex]E(Y| X=1)= E(1|X=1) + E(X|X=1) + E(u|X=1) = E(1) + 1 + E(v) + 0 = 1+1+0=2[/tex]
c) [tex] E(u|X=2)= E(v|X=2) + E(X|X=2) = E(v) +2 = 0 +2 =2[/tex]
d) [tex]E(Y| X=2)= E(1|X=2) + E(X|X=2) + E(u|X=2) = E(2) + 2 + E(v) + 2 = 2+2+2=6[/tex]
e) [tex] E(u|X) = E(v+X |X) = E(v|X) +E(X|X) = E(v) +E(X) = 0+1=1[/tex]
f) [tex] E(Y|X) = E(1+X+u |X) = E(1|X) +E(X|X) + E(u|X) = 1+1+1=3[/tex]
g) [tex]E(u) = E(v) +E(X) = 0+1=1[/tex]
h) E(Y) = E(1+X+u) = E(1) + E(X) +E(v+X) = 1+1 + E(v) +E(X) = 1+1+0+1 = 3[/tex]
Step-by-step explanation:
For this case we know this:
[tex] Y = 1+X +u[/tex]
[tex] u = v+X[/tex]
with both Y and u random variables, we also know that:
[tex] [tex] E(v) = 0, Var(v) =1, E(X) = 1, Var(X)=2[/tex]
And we want to calculate this:
Part a
[tex] E(u|X=1)= E(v+X|X=1)[/tex]
Using properties for the conditional expected value we have this:
[tex] E(u|X=1)= E(v|X=1) + E(X|X=1) = E(v) +1 = 0 +1 =1[/tex]
Because we assume that v and X are independent
Part b
[tex]E(Y| X=1) = E(1+X+u|X=1)[/tex]
If we distribute the expected value we got:
[tex]E(Y| X=1)= E(1|X=1) + E(X|X=1) + E(u|X=1) = E(1) + 1 + E(v) + 0 = 1+1+0=2[/tex]
Part c
[tex] E(u|X=2)= E(v+X|X=2)[/tex]
Using properties for the conditional expected value we have this:
[tex] E(u|X=2)= E(v|X=2) + E(X|X=2) = E(v) +2 = 0 +2 =2[/tex]
Because we assume that v and X are independent
Part d
[tex]E(Y| X=2) = E(1+X+u|X=2)[/tex]
If we distribute the expected value we got:
[tex]E(Y| X=2)= E(1|X=2) + E(X|X=2) + E(u|X=2) = E(2) + 2 + E(v) + 2 = 2+2+2=6[/tex]
Part e
[tex] E(u|X) = E(v+X |X) = E(v|X) +E(X|X) = E(v) +E(X) = 0+1=1[/tex]
Part f
[tex] E(Y|X) = E(1+X+u |X) = E(1|X) +E(X|X) + E(u|X) = 1+1+1=3[/tex]
Part g
[tex]E(u) = E(v) +E(X) = 0+1=1[/tex]
Part h
E(Y) = E(1+X+u) = E(1) + E(X) +E(v+X) = 1+1 + E(v) +E(X) = 1+1+0+1 = 3[/tex]
Determine the parametric equations of the position of a particle with constant velocity that follows a straight line path on the plane if it starts at the point P(7,2) and after one second it is at the point Q(2,7).
The parametric equations of the position of a particle with constant velocity moving along a straight line path from points P(7,2) to Q(2,7) are x(t) = 7 - 5t and y(t) = 2 + 5t.
Explanation:In this context, the movement of a particle can be represented on a plane using a usual 2D Cartesian coordinate system. The constant velocity of the particle dictates it will always move along a straight line. The straight line path can be found by determining the slope between points P(7,2) and Q(2,7).
The slope m of the line is given by:
m = (y2 - y1) / (x2 - x1)
Where P = (x1, y1) and Q= (x2, y2). Applying these coordinates gives us:
m = (7 - 2) / (2 - 7) = -1
So, the line equation we have is something like y - y1 = m(x - x1), and substituting in all the values gives:
y - 2 = -1 * (x - 7) which simplifies to y = -x + 9
To get the parametric equations, we can consider the particle moving along the straight line path from P to Q in time t = 1 second. The parametric equations of the position of the particle is therefore:
x(t) = 7 - 5t and y(t) = 2 + 5t
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A recent article reported that a job awaits only one in three new college graduates. (1 in 3 means the proportion is .333) A survey of 200 recent graduates revealed that 80 graduates had jobs. At the .02 significance level, we will conduct a hypothesis test to determine if we can conclude if a larger proportion of graduates have jobs than previously reported.
a.What will be the value of our critical value?
b.What will be the value of our test statistic?
c.can we conclude that a larger proportion of graduates have jobs than reported in the article?
Answer:
a) [tex]2.05[/tex]
b) [tex]z = 2.01[/tex]
c) No, we cannot conclude that a larger proportion of graduates have jobs than reported in the article.
Step-by-step explanation:
We are given the following in the question:
Sample size, n = 200
p = 0.333
Alpha, α = 0.02
Number of graduates had jobs , x = 80
First, we design the null and the alternate hypothesis
[tex]H_{0}: p = 0.333\\H_A: p > 0.333[/tex]
This is a one-tailed(right) test.
b) Formula:
[tex]\hat{p} = \dfrac{x}{n} = \dfrac{80}{200} = 0.4[/tex]
[tex]z = \dfrac{\hat{p}-p}{\sqrt{\dfrac{p(1-p)}{n}}}[/tex]
Putting the values, we get,
a) [tex]z = \displaystyle\frac{0.4-0.333}{\sqrt{\frac{0.333(1-0.333)}{200}}} = 2.01[/tex]
Now, [tex]z_{critical} \text{ at 0.02 level of significance } = 2.05[/tex]
c) Since, the calculated z statistics less than the critical value, we fail to reject the null hypothesis and accept it.
Thus, same proportion of graduates have jobs as compared to previously reported.
Thus, we conclude that there is not enough evidence to support the claim that a larger proportion of graduates have jobs than previously reported.
A baseball leaves the hand of a pitcher 6 vertical feet above home plate and 60 feet from home plate. Assume the x-axis is a straight on the flat ground from mound to the plate, the y-axis lies on the groundfrom the 3rd to 1st base and the z axis is vertical height.
(a) In the absence of all forces except gravity, assume that a pitch is thrown with an initial velocity of 130i +0j-3k ft/s (roughly 90mi/hr). How far above the ground is the ball when it cross the home plate.
(b) How long does it take for the pitch to arrive at home plate?
(c) what vertical velocity component should the pitcher use so that the pitch crosses home plate exactly 3 feet above the ground?
(d) A simple model to describe the curve of the baseball assumes that the spin of the ball produces a constant acceleration (in the y direction) of c ft/s^(2). Assume a pitcher throws a curve ball with c=8ft/s^(2) (1/4 the acceleration of gravity). how far does the ball move inthe y-directionby the time it reaches home plate, assuming an initial velocity of 130i +0j -3k ft/s ?
(e) Using the above information, does the ball curve more in the first half of its trip to second or in the second half?
(f) How does this effect better?
(g) Suppose the pitcher releases the ball from an initial position of <0,-3,6> with an initial velocity of 130i +0j-3k. What value of the spin parameter c is needed to put the ball over home plater passing through the point <60,0,3>?
In the absence of all forces except gravity, the ball is approximately 0.28 feet below the ground when it crosses the home plate.
Explanation:(a) In the absence of all forces except gravity, assume that a pitch is thrown with an initial velocity of 130i +0j-3k ft/s (roughly 90mi/hr). How far above the ground is the ball when it cross the home plate.
To determine the vertical distance the ball is above the ground when it crosses home plate, we need to find the time it takes to reach the home plate using the vertical component of the initial velocity. The initial vertical velocity is -3 ft/s, and the vertical acceleration due to gravity is -32 ft/s2. Using the equation y = y0 + v0yt + 0.5at2, where y is the vertical distance above the ground, y0 is the initial vertical position, v0y is the initial vertical velocity, t is the time, and a is the acceleration due to gravity, we can solve for t. Plugging in the given values, we get:
y = 0 + (-3)t + 0.5(-32)t2
Simplifying the equation, we get 32t2 - 3t = 0. Factoring out t, we get t(32t - 3) = 0. So, either t = 0 (which is the initial time when the ball is released) or 32t - 3 = 0. Solving for t, we find that t = 3/32 seconds. Since the ball is in the air for this amount of time, we can substitute this value back into the equation to find the vertical distance above the ground when the ball crosses the home plate:
y = 0 + (-3)(3/32) + 0.5(-32)(3/32)2
Simplifying, we get y = -9/32 feet, which is approximately -0.28 feet above the ground. Therefore, the ball is 0.28 feet below the ground when it crosses the home plate.
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What does the cross product between two vectors represent, and what are some of its properties
Answer:
See explanation below.
Step-by-step explanation:
Definition
The cross product is a binary operation between two vectors defined as following:
Let two vectors [tex] a = (a_1 ,a_2,a_3) , b=(b_1, b_2, b_3)[/tex]
The cross product is defined as:
[tex] a x b = (a_2 b_3 -a_3 b_2, a_3 b_1 -a_1 b_3 ,a_1 b_2 -a_2 b_1)[/tex]
The last one is the math definition but we have a geometric interpretation as well.
We define the angle between two vectors a and b [tex]\theta[/tex] and we assume that [tex] 0\leq \theta \leq \pi[/tex] and we have the following equation:
[tex] |axb| = |a| |b| sin(\theta)[/tex]
And then we conclude that the cross product is orthogonal to both of the original vectors.
Some properties
Let a and b vectors
If two vectors a and b are parallel that implies [tex] |axb| =0[/tex]
If [tex] axb \neq 0[/tex] then [tex]axb[/tex] is orthogonal to both a and b.
Let u,v,w vectors and c a scalar we have:
[tex] uxv =-v xu[/tex]
[tex] ux (v+w) = uxv + uxw[/tex] (Distributive property)
[tex] (cu)xv = ux(cv) =c (uxv)[/tex]
[tex] u. (vxw) = (uxv).w[/tex]
Other application of the cross product are related to find the area of a parallelogram for two dimensions where:
[tex] A = |axb|[/tex]
And when we want to find the volume of a parallelepiped in 3 dimensions:
[tex] V= |a. (bxc)|[/tex]
The null hypothesis is that the true proportion of the population is equal to .40. A sample of 120 observations revealed the sample proportion "p" was equal to .30. At the .05 significance level test to see if the true proportion is in fact different from .40.
(a) What will be the value of the critical value on the left?
(b) What is the value of your test statistic?
(c) Did you reject the null hypothesis?
(d) Is there evidence that the true proportion is different from .40?
Answer:
There is enough evidence to support the claim that the true proportion is in fact different from 0.40
Step-by-step explanation:
We are given the following in the question:
Sample size, n = 120
p = 0.4
Alpha, α = 0.05
First, we design the null and the alternate hypothesis
[tex]H_{0}: p = 0.4\\H_A: p \neq 0.4[/tex]
This is a two-tailed test.
Formula:
[tex]\hat{p} = 0.3[/tex]
[tex]z = \dfrac{\hat{p}-p}{\sqrt{\dfrac{p(1-p)}{n}}}[/tex]
Putting the values, we get,
[tex]z = \displaystyle\frac{0.3-0.4}{\sqrt{\frac{0.4(1-0.4)}{120}}} = -2.236[/tex]
Now, [tex]z_{critical} \text{ at 0.05 level of significance } = \pm 1.96[/tex]
Since,
The calculated z-statistic does not lies in the acceptance region, we fail to accept the null hypothesis and reject it. We accept the alternate hypothesis.
Thus, there is enough evidence to support the claim that the true proportion is in fact different from 0.40
Consider the simple linear regression model Yi=β0+β1xi+ϵi, where ϵi's are independent N(0,σ2) random variables. Therefore, Yi is a normal random variable with mean β0+β1xi and variance σ2. Moreover, Yi's are independent. As usual, we have the observed data pairs (x1,y1), (x2,y2), ⋯⋯, (xn,yn) from which we would like to estimate β0 and β1. In this chapter, we found the following estimators β1^=sxysxx,β0^=Y¯¯¯¯−β1^x¯¯¯. where sxx=∑i=1n(xi−x¯¯¯)2,sxy=∑i=1n(xi−x¯¯¯)(Yi−Y¯¯¯¯). Show that β1^ is a normal random variable. Show that β1^ is an unbiased estimator of β1, i.e., E[β1^]=β1. Show that Var(β1^)=σ2sxx.
Answer:
See proof below.
Step-by-step explanation:
If we assume the following linear model:
[tex] y = \beta_o + \beta_1 X +\epsilon[/tex]
And if we have n sets of paired observations [tex] (x_i, y_i) , i =1,2,...,n[/tex] the model can be written like this:
[tex] y_i = \beta_o +\beta_1 x_i + \epsilon_i , i =1,2,...,n[/tex]
And using the least squares procedure gives to us the following least squares estimates [tex] b_o [/tex] for [tex]\beta_o[/tex] and [tex] b_1[/tex] for [tex]\beta_1[/tex] :
[tex] b_o = \bar y - b_1 \bar x[/tex]
[tex] b_1 = \frac{s_{xy}}{s_xx}[/tex]
Where:
[tex] s_{xy} =\sum_{i=1}^n (x_i -\bar x) (y-\bar y)[/tex]
[tex] s_{xx} =\sum_{i=1}^n (x_i -\bar x)^2[/tex]
Then [tex] \beta_1[/tex] is a random variable and the estimated value is [tex]b_1[/tex]. We can express this estimator like this:
[tex] b_1 = \sum_{i=1}^n a_i y_i [/tex]
Where [tex] a_i =\frac{(x_i -\bar x)}{s_{xx}}[/tex] and if we see careful we notice that [tex] \sum_{i=1}^n a_i =0[/tex] and [tex]\sum_{i=1}^n a_i x_i =1[/tex]
So then when we find the expected value we got:
[tex] E(b_1) = \sum_{i=1}^n a_i E(y_i)[/tex]
[tex] E(b_1) = \sum_{i=1}^n a_i (\beta_o +\beta_1 x_i)[/tex]
[tex] E(b_1) = \sum_{i=1}^n a_i \beta_o + \beta_1 a_i x_i[/tex]
[tex] E(b_1) = \beta_1 \sum_{i=1}^n a_i x_i = \beta_1[/tex]
And as we can see [tex]b_1[/tex] is an unbiased estimator for [tex]\beta_1[/tex]
In order to find the variance for the estimator [tex]b_1[/tex] we have this:
[tex] Var(b_1) = \sum_{i=1}^n a_i^2 Var(y_i) +\sum_i \sum_{j \neq i} a_i a_j Cov (y_i, y_j) [/tex]
And we can assume that [tex] Cov(y_i,y_j) =0[/tex] since the observations are assumed independent, then we have this:
[tex] Var (b_1) =\sigma^2 \frac{\sum_{i=1}^n (x_i -\bar x)^2}{s^2_{xx}}[/tex]
And if we simplify we got:
[tex] Var(b_1) = \frac{\sigma^2 s_{xx}}{s^2_{xx}} = \frac{\sigma^2}{s_{xx}}[/tex]
And with this we complete the proof required.
Final answer:
β1^ in simple linear regression is normal because it is a ratio of linear combinations of normal variables Yi. It is unbiased as its expected value equals the true parameter β1. The variance of β1^ is σ2/sxx, derived from properties of variance and the independent nature of errors ϵi.
Explanation:
The student's question pertains to the properties of the estimated coefficient β1^ in a simple linear regression model. To show that β1^ is a normal random variable, we consider the linear combination of the normal random variables Yi, because a linear combination of normal random variables is also normally distributed. Since each Yi is normal and given by Yi=β0+β1xi+ϵi, and ϵi is N(0,σ2), the estimator β1^=sxy/sxx becomes a ratio of linear combinations of these normal variables and hence, normal.
Next, to prove that β1^ is an unbiased estimator, we take the expectation of β1^ and show that E[β1^]=β1. It's implied by calculating the expected value of the numerator sxy and denominator sxx separately and showing the ratio equals β1.
The variance of β1^, Var(β1^), can be shown to be σ2/sxx by leveraging properties of variance of the linear combinations of Yi and noting that ϵi's are independent random variables with variance σ2. The calculations involve squaring the deviations and utilizing expectations.