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Paired or unpaired? In each of the following settings, decide whether you should use paired t procedures or two-sample t procedures to perform inference. Explain your choice. 42

(a) To test the wear characteristics of two tire brands, A and B, each brand of tire is randomly assigned to 50 cards of the same make and model.

(b) To test the effect of background music on productivity, factory workers are observed. For one month, each subject works without music. For another month, the subject works while listening to music on an MP3 player. The month in which each subject listens to music is determined by a coin toss.

(c) A study was designed to compare the effectiveness of two weight-reducing diets. Fifty obese women who volunteered to participate were randomly assigned into two equal-sized groups. One group used Diet \(A\) and the other used Diet B. The weight of each woman was measured before the assigned diet and

Short Answer

Expert verified

a)Two-samples procedures

b) Paired t procedures

c)Two-sample t procedures

Step by step solution

01

Part (a) Step 1: Given Information

To determine whether paired t-test or two-sample t-test should be used to conduct inference on the basis of the information provided.

02

Part(a) Step 2: Explanation

If each value in one sample has an associating value in the other sample, paired ttechniques are used; otherwise, two-sample tprocedures are used.

toperations with two samples

Because each sample contains a different set of tyres.

03

Part (b) Step 1: Given Information

To determine whether paired t-test or two-sample t-test should be used to conduct inference on the basis of the information provided.

04

Part (b) Step 2: Explanation

If a value in one sample has an associating value in another, paired tprocedures are employed; otherwise, two-sample ttechniques are utilised.

toperations that are paired.

Because every subject is represented in both samples.

05

Part (c) Step 1: Given Information

To determine whether paired t-test or two-sample t-test should be used to conduct inference on the basis of the information provided.

06

Part (c) Step 2: Explanation

If a value in one sample has a corresponding value in the other, we utilize paired tmethods; otherwise, we use two-sample tprocedures.

toperations with two samples

Because each sample has a large number of individuals,

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Most popular questions from this chapter

A study of road rage asked separate random samples of 596men and 523women about their behavior while driving. Based on their answers, each re-spondent was assigned a road rage score on a scale of 0to 20. Are the conditions for performing a two-sample t test satisfied?

a) Maybe; we have independent random samples, but we need to look at the data to check Normality.

(b) No; road rage scores in a range between 0 and 20 canโ€™t be Normal.

(c) No; we donโ€™t know the population standard deviations.

(d) Yes; the large sample sizes guarantee that the corresponding population distributions will be Normal.

(e) Yes; we have two independent random samples and large sample sizes.

T10.11. Researchers wondered whether maintaining a patient's body temperature close to normal by heating the patient during surgery would affect wound infection rates. Patients were assigned at random to two groups: the normothermic group (patients' core temperatures were maintained at near normal, 36.5ยฐC, with heating blankets) and the hypothermic group (patients" core temperatures were allowed to decrease to about34.5ยฐC). If keeping patients warm during surgery alters the chance of infection, patients in the two groups should have hospital stays of very different lengths. Here are summary statistics on hospital stay (in number of days) for the two groups:

GroupnxยฏsxNormothemic10412.14.4Hypothermic9614.76.5

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

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

According to sleep researchers, if you are between the ages of 12and18years old, you need 9hours of sleep to be fully functional. 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?

(a) H0:ฮผ=7.9andHa:ฮผ<7.9

(b) H0:ฮผ=7.9andHa:ฮผโ‰ 7.9

(c) H0:ฮผ=9andHa:ฮผโ‰ 9

(d)H0:ฮผ=9andHa:ฮผ<9

(e)H0:ฮผโ‰ค9andHa:ฮผโ‰ฅ9

Explain why the conditions for using two-sample z procedures to perform inference about p1-p2are not met in the settings

Donโ€™t drink the water! The movie A Civil Action (Touchstone Pictures 1998) tells the story of a major legal battle that took place in the small town of Woburn, Massachusetts. A town well that supplied water to eastern Woburn residents was contaminated by industrial chemicals. During the period that residents drank water from this well, 16of the 414babies born had birth defects. On the west side of Woburn, 3of the 228babies born during the same time period had birth defects.

46. Happy customers As the Hispanic population in the United States has grown, businesses have tried to understand what Hispanics like. One study inter-viewed a random sample of customers leaving a bank. Customers were classified as Hispanic if they preferred to be interviewed in Spanish or as Anglo if they preferred English. Each customer rated the importance
of several aspects of bank service on a 10-point scale. Here are summary results for the importance of โ€œreliabilityโ€ (the accuracy of account records and so on):

(a) The distribution of reliability ratings in each group is not Normal. A graph of the data reveals no outliers. The use of two-sample t procedures is
justified. Why?
(b) Construct and interpret a 95% confidence interval for the difference between the mean ratings of the importance of reliability for Anglo and
Hispanic bank customers.
(c) Interpret the 95% confidence level in the context of this study.

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