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Refer to Exercise 38.

a. Find the probability of getting a difference in sample means x炉M鈭抶炉WxM-xWthat鈥檚 greater than 2inches.

b. Should we be surprised if the sample mean height for the young men is at least2 inches greater than the sample mean height for the young women? Explain your answer.

Short Answer

Expert verified

Part a. The probability is 0.9949

Part b. No.

Step by step solution

01

Part a. Step 1. Given information

From the previous exercise, we have:

=4.8=1.0883x=2

02

Part a. Step 2. Explanation

The z score is the value decreased by the mean and divided by the standard deviation. Then we have,

z=x-=2-4.81.0883=-2.57

Now we will determine the value of the probability, that is:

P(xM-xW2)=P(Z>-2.57)=1-P(Z<-2.57)=1-0.0051=0.9949=00.49%

03

Part b. Step 1. Explanation

It is given that:

z=x-=2-4.81.0883=-2.57

And the probability is 0.9949.

Thus, a probability is considered to be small when the probability is less than 0.05.

We then note that the probability of the mean differencexM-xW being at least two is large which means that it is unlikely that the mean difference is at least two and thus we would be not be surprised if the sample mean height for the young men is at least two inches greater than the sample mean height for the young women. Thus, we should not be surprised.

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Most popular questions from this chapter

A 96% confidence interval for the proportion of the labor force that is unemployed in a certain city is (0.07,0.10). Which of the following statements is true?

a. The probability is 0.96 that between 7%and10% of the labor force is unemployed.

b. About 96% of the intervals constructed by this method will contain the true proportion of the labor force that is unemployed in the city.

c. In repeated samples of the same size, there is a 96% chance that the sample proportion will fall between 0.07and0.10.

d. The true rate of unemployment in the labor force lies within this interval 96% of the time.

e. Between 7%and10%of the labor force is unemployed 96% of the time.

A researcher wished to compare the average amount of time spent in extracurricular activities by high school students in a suburban school district with that in a school district of a large city. The researcher obtained an SRS of 60 high school students in a large suburban school district and found the mean time spent in extracurricular activities per week to be 6 hours with a standard deviation of 3 hours. The researcher also obtained an independent SRS of 40 high school students in a large city school district and found the mean time spent in extracurricular activities per week to be 5 hours with a standard deviation of 2 hours. Suppose that the researcher decides to carry out a significance test of H0:suburban=cityversus a two-sided alternative. Which is the correct standardized test statistic ?

(a)z=(6-5)-0360+240

(b) z=(6-5)-03260+2240

(c) role="math" localid="1654192807425" t=(6-5)-0360+240

(d) t=(6-5)-0360+240

(e)t=(6-5)-03260+2240


The P-value for the stated hypotheses is 0.002Interpret this value in the context of this study.

a. Assuming that the true mean road rage score is the same for males and females, there is a 0.002probability of getting a difference in sample means equal to the one observed in this study.

b. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability of getting a difference in sample means at least as large in either direction as the one observed in this study.

c. Assuming that the true mean road rage score is different for males and females, there is a 0.002 probability of getting a difference in sample means at least as large in either direction as the one observed in this study.

d. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability that the null hypothesis is true.

e. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability that the alternative hypothesis is true.

Ban junk food! A CBS News poll asked 606 randomly selected women and 442

randomly selected men, 鈥淒o you think putting a special tax on junk food would encourage more people to lose weight?鈥 170 of the women and 102 of the men said 鈥淵es.鈥 A 99% confidence interval for the difference (Women 鈥 Men) in the true proportion of people in each population who would say 鈥淵es鈥 is 鈭0.020to0.120. Does the confidence interval provide convincing evidence that the two population proportions are equal? Explain your answer.

Have a ball! Can students throw a baseball farther than a softball? To find out, researchers conducted a study involving 24randomly selected students from a large high school. After warming up, each student threw a baseball as far as he or she could and threw a softball as far as he she could, in a random order. The distance in yards for each throw was recorded. Here are the data, along with the difference (Baseball 鈥 Softball) in distance thrown, for each student:

a. Explain why these are paired data.

b. A boxplot of the differences is shown. Explain how the graph gives some evidence that students like these can throw a baseball farther than a softball.

c. State appropriate hypotheses for performing a test about the true mean difference. Be sure to define any parameter(s) you use.

d. Explain why the Normal/Large Sample condition is not met in this case. The mean difference (Baseball鈭扴oftball) in distance thrown for these 24students is xdiff = 6.54yards. Is this a surprisingly large result if the null hypothesis is true? To find out, we can perform a simulation assuming that students have the same ability to throw a baseball and a softball. For each student, write the two distances thrown on different note cards. Shuffle the two cards and designate one distance to baseball and one distance to softball. Then subtract the two distances (Baseball鈭扴oftball) . Do this for all the students and find the simulated mean difference. Repeat many times. Here are the results of 100trials of this simulation

e. Use the results of the simulation to estimate the P-value. What conclusion would you draw ?

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