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Two samples or paired data? In each of the following settings, decide whether you should use two-sample t procedures to perform inference about a difference in means or paired t procedures to perform inference about a mean difference. Explain your choice.

a. To test the wear characteristics of two tire brands, A and B, each of 50cars of the same make and model is randomly assigned Brand A tires or Brand B tires.

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. How do young adults look back on adolescent romance? Investigators interviewed a random sample of 40couples in their mid-twenties. The female and male partners were interviewed separately. Each was asked about his or her current relationship and also about a romantic relationship that lasted at least 2months when they were aged 15or 16. One response variable was a measure on a numerical scale of how much the attractiveness of the adolescent partner mattered. You want to find out how much men and women differ on this measure.

Short Answer

Expert verified

Part(a) We should use two-sample t procedures to perform inference about a difference in means.

Part(b) We should use paired t procedures to perform inference about a mean difference.

Part(c) We should use paired t procedures to perform inference about a mean difference.

Step by step solution

01

Part(a) Step 1 : Given information

We need to decide whether to use two-sample t procedures or paired t procedures to check inference about a mean difference.

02

Part(a) Step 2 : Simplify

We must use paired t techniques if the two samples contain the same individuals or if the subjects in one sample are related to the subjects in the other sample.
We must use two sample t techniques if the subjects in the two samples are completely unrelated.
Automobiles are randomly assigned to either brand A or brand B in this scenario, resulting in a first sample of brand A cars and a second sample of brand B cars.
Because the cars were randomly assigned to one of the samples, the cars in the two samples will be completely unrelated, making the two sample t methods suitable.


03

Part(b) Step 1 : Given information

We need to decide whether we should use two-sample t procedures to perform inference about a difference in means or paired t procedures to perform inference about a mean difference.

04

Part(b) Step 2 : Simplify

If the two samples contain the same individuals or if the subjects in one sample are connected to the subjects in the other sample, we must employ paired t methods.
If the subjects in the two samples are fully unrelated, we must employ two sample t methods.
For one month, each topic worked with music and for one month, each subject worked without music.
The data for all participants who worked with music for one month is the first sample, while the data for all subjects who worked without music for one month is the second sample.
We should utilise paired t methods because the two samples are the same subjects.

05

Part(c) Step 1 : Given information

We need to decide whether we should use two-sample t procedures to perform inference about a difference in means or paired t procedures to perform inference about a mean difference.

06

Part(c) Step 2 : Simplify

If the two samples contain the same individuals or if the subjects in one sample are connected to the subjects in the other sample, we must employ paired t methods.
If the subjects in the two samples are fully unrelated, we must employ two sample t methods.
We questioned the male and female partners separately in each of the 40couples.
The male partners are in the first sample, while the female partners are in the second.
Because all of the participants in the first sample are male spouses of a subject in the second sample, we should utilise the paired t methods to compare the two samples.

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Most popular questions from this chapter

A large university is considering the establishment of a schoolwide recycling program. To gauge interest in the program by means of a questionnaire, the university takes separate random samples of undergraduate students, graduate students, faculty, and staff. This is an example of what type of sampling design?

a. Simple random sample

b. Stratified random sample

c. Convenience sample

d. Cluster sample

e. Randomized block design

Shortly before the 2012presidential election, a survey was taken by the school newspaper at a very large state university. Randomly selected students were asked, 鈥淲hom do you plan to vote for in the upcoming presidential election?鈥 Here is a two-way table of the responses by political persuasion for 1850students:

Candidate of

choice


Political persuasion

Democrat
Republican
Independent
Total
Obama
925
78
26
1029
Romney
78
598
19
695
Other
2
8
11
21
Undecided
32
28
45
105
Total
1037
712
101
1850

Which of the following statements about these data is true?

a. The percent of Republicans among the respondents is 41%.

b. The marginal relative frequencies for the variable choice of candidate are given by

Obama: 55.6%; Romney: 37.6%; Other: 1.1%; Undecided: 5.7%.

c. About 11.2%of Democrats reported that they planned to vote for Romney.

d. About 44.6%of those who are undecided are Independents.

e. The distribution of political persuasion among those for whom Romney is the

candidate of choice is Democrat: 7.5%; Republican: 84.0%; Independent: 18.8%.

Suppose the true proportion of people who use public transportation to get to work in the Washington, D.C. area is 0.45. In a simple random sample of 250people who work in Washington, about how far do you expect the sample proportion to be from the true proportion?

a. 0.4975

b. 0.2475

c. 0.0315

d. 0.0009

e.0

Literacy Refer to Exercise 2.

a. Find the probability that the proportion of graduates who pass the test is at most 0.20higher than the proportion of dropouts who pass, assuming that the researcher鈥檚 report is correct.

b. Suppose that the difference (Graduate 鈥 Dropout) in the sample proportions who pass the test is exactly 0.20. Based on your result in part (a), would this give you reason to doubt the researcher鈥檚 claim? Explain your reasoning.

Young adults living at home A surprising number of young adults (ages 19

to 25) still live in their parents鈥 homes. The National Institutes of Health surveyed

independent random samples of 2253men and 2629women in this age group. The survey found that 986 of the men and 923 of the women lived with their parents.

a. Construct and interpret a 99%confidence interval for the difference in the true

proportions of men and women aged 19-25who live in their parents鈥 homes.

b. Does your interval from part (a) give convincing evidence of a difference between the population proportions? Justify your answer.

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