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Does music help or hinder memory? Many students at Matt’s school claim they can think more clearly while listening to their favorite kind of music. Matt believes that music interferes with thinking clearly. To find out which is true, Matt recruits 84 volunteers and randomly assigns them to two groups. The “Music” group listens to their favorite music while playing a “match the animals” memory game. The “No Music” group plays the same game in silence. Here are some descriptive statistics for the number of turns it took

the subjects in each group to complete the game (fewer turns indicate better performance):

Matt wants to know if listening to music affects the average number of turns required to finish the memory game for students like these.

a. State appropriate hypotheses for performing a significance test. Be sure to define the parameters of interest.

b. Check if the conditions for performing the test are met.

Short Answer

Expert verified

Part a) The hypotheses are:

H0:μ1=μ2Ha:μ1notequaltoμ2

Part b) All condtions are met.

Step by step solution

01

Part a) Step 1: Given information

The given claim is that a difference in the means.

02

Part b) Explanation

We must now determine the appropriate hypotheses for performing a significance test.

As a result, the claim represents either the null hypothesis or the alternative hypothesis. According to the null hypothesis, the population proportions are equal. If the claim is the null hypothesis, then the alternative hypothesis states the inverse of the null hypothesis.

Therefore, the appropriate hypotheses for this are:

H0:μ1=μ2Ha:μ1notequaltoμ2

μ1=the true mean number of turns required to complete the memory game for music-listening students.

For students who do not listen to music, μ2 is the true mean number of turns required to complete the memory game.

03

Part b) Step 1: Explanation

There are three requirements that must be met:

It is satisfying because the samples are drawn at random from different populations.

Independent: It is satisfying because the sample of 42people represents less than 10%of the total population.

Normal: It is satisfied because both samples are large, with sample sizes of at least 30.

As a result, all of the conditions are met, and a hypothesis test for the mean difference is appropriate.

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Most popular questions from this chapter

Researchers wondered whether maintaining a patient’s body temperature close to normal by heating the patient during surgery would affect rates of infection of wounds. Patients were assigned at random to two groups: the normothermic group (core temperatures were maintained at near normal, 36.5°C, using heating blankets) and the hypothermic group (core temperatures were allowed to decrease to about 34.5°C). If keeping patients warm during surgery alters the chance of infection, patients in the two groups should show a difference in the average length of their hospital stays. Here are summary statistics on hospital stay (in number of days) for the two groups:

a. Construct and interpret a 95%confidence interval for the difference in the true mean length of hospital stay for normothermic and hypothermic patients like these.

b. Does your interval in part (a) suggest that keeping patients warm during surgery affects the average length of patients’ hospital stays? Justify your answer.

c. Interpret the meaning of “95%confidence” in the context of this study.

On your mark In track, sprinters typically use starting blocks because they think it will help them run a faster race. To test this belief, an experiment was designed where each sprinter on a track team ran a 50-meter dash two times, once using starting blocks and once with a standing start. The order of the two different types of starts was determined at random for each sprinter. The times (in seconds) for 8 different sprinters are shown in the table.

a. Make a dotplot of the difference (Standing - Blocks) in 50-meter run time for each sprinter. What does the graph suggest about whether starting blocks are helpful?

b. Calculate the mean difference and the standard deviation of the differences. Explain why the mean difference gives some evidence that starting blocks are helpful.

c. Do the data provide convincing evidence that sprinters like these run a faster race when using starting blocks, on average?

d. Construct and interpret a 90%confidence interval for the true mean difference. Explain how the confidence interval gives more information than the test in part (b).

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 60high school students in a large suburban school district and found the mean time spent in extracurricular activities per week to be 6hours with a standard deviation of 3hours. The researcher also obtained an independent SRS of 40high school students in a large city school district and found the mean time spent in extracurricular activities per week to be 5hours with a standard deviation of 2hours. Suppose that the researcher decides to carry out a significance test of H0: μsuburban=μcity versus a two-sided alternativ

The P-value for the test is 0.048. A correct conclusion is to

a. fail to reject H0because0.048<α=0.05. There is convincing evidence of a difference in the average time spent on extracurricular activities by students in the suburban and city school districts.

b. fail to reject H0because 0.048<α=0.05. There is not convincing evidence of a difference in the average time spent on extracurricular activities by students in the suburban and city school districts.

c. fail to reject H0because0.048<α=0.05. There is convincing evidence that the average time spent on extracurricular activities by students in the suburban and city school districts is the same.

d. reject H0because 0.048<α=0.05. There is not convincing evidence of a difference in the average time spent on extracurricular activities by students in the suburban and city school districts.

e. reject H0because 0.048<α=0.05 . There is convincing evidence of a difference in the average time spent on extracurricular activities by students in the suburban and city school districts.

According to sleep researchers, if you are between the ages of 12and 18years old, you need 9hours of sleep to function well. A simple random sample of 28students was chosen from a large high school, and these students were asked how much sleep they got the previous night. The mean of the responses was 7.9hours with a standard deviation of 2.1hours. If we are interested in whether students at this high school are getting too little sleep, which of the following represents the appropriate null and alternative hypotheses ?

  1. H0:μ=7.9and Ha:μ<7.9
  2. H0:μ=7.9and Ha:μ7.9
  3. H0:μ=9and Ha:μ9
  4. H0:μ=9and width="69" height="24" role="math">Ha:μ<9
  5. H0:μ9andHa:μ9

I want red! Refer to Exercise 1.

a. Find the probability that the proportion of red jelly beans in the Child sample is less than or equal to the proportion of red jelly beans in the Adult sample, assuming that the company’s claim is true.

b. Suppose that the Child and Adult samples contain an equal proportion of red jelly beans. Based on your result in part (a), would this give you reason to doubt the

company’s claim? Explain your reasoning.

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