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Chapter 4: Q. 1 (page 236)

Sampling stuffed envelopes A large retailer prepares its customers’

monthly credit card bills using an automatic machine that folds the bills, stuffs them into

envelopes, and seals the envelopes for mailing. Are the envelopes completely sealed?

Inspectors choose 40envelopes at random from the 1000stuffed each hour for visual

inspection. Identify the population and the sample.

Short Answer

Expert verified

Population: all local businesses.

Sample : 40.

Step by step solution

01

Given information

We have to find the population and sample.

02

Explanation

A sample survey picks a group of people from a larger group of people about whom we wish to learn more.

Population: all local businesses.

Sample : 40.

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Most popular questions from this chapter

Eating on campus The director of student life at a small college wants to know what

percent of students eat regularly in the cafeteria. To find out, the director selects an SRS of

300 students who live in the dorms. Describe how undercoverage might lead to bias in this

study. Explain the likely direction of the bias.

Layoffs and “survivor guilt” Workers who survive a layoff of other employees at their location may suffer from “survivor guilt.” A study of survivor guilt and its effects used as subjects 120students who were offered an opportunity to earn extra course credit by doing proofreading. Each subject worked in the same cubicle as another student, who was an accomplice of the experimenters. At a break midway through the work, one of three things happened:

Treatment 1: The accomplice was told to leave; it was explained that this was because she performed poorly.

Treatment 2: It was explained that unforeseen circumstances meant there was only enough work for one person. By “chance,” the accomplice was chosen to be laid off.

Treatment 3: Both students continued to work after the break. The subjects’ work performance after the break was compared with their performance before the break. Overall, subjects worked harder when told the other student’s dismissal was random.

Describe how you would randomly assign the subjects to the treatments

a. using slips of paper.

b. using technology.

c. using Table D.

In the experiment of the preceding exercise, the subjects were randomly assigned to the

different treatments. What is the most important reason for this random assignment?

a. Random assignment eliminates the effects of other variables such as stress and body

weight.

b. Random assignment is a good way to create groups of subjects that are roughly

equivalent at the beginning of the experiment.

c. Random assignment makes it possible to make a conclusion about all men.

d. Random assignment reduces the amount of variation in blood pressure.

e. Random assignment prevents the placebo effect from ruining the results of the study.

How is your room? A hotel has 30floors with 40rooms per floor. The rooms on one side of the hotel face the water, while rooms on the other side face a golf course. There is an extra charge for the rooms with a water view. The hotel manager wants to select 120rooms and survey the registered guest in each of the selected rooms about his or her overall satisfaction with the property.

a. Describe how to obtain a sample of 120rooms using stratified random sampling. Explain your choice of strata and why this method might be preferred to simple random sampling.

b. Describe how to obtain a sample of 120rooms using cluster sampling. Explain your choice of clusters and why this method might be preferred to simple random sampling.

Tonya wanted to estimate the average amount of time that students at her school spend on Facebook each day. She gets an alphabetical roster of students in the school from the registrar’s office and numbers the students from 1 to 1137. Then Tonya uses a random number generator to pick 30 distinct labels from 1 to 1137. She surveys those 30 students about their Facebook use. Tonya’s sample is a simple random sample because

a. it was selected using a chance process.

b. it gave every individual the same chance to be selected.

c. it gave every possible sample of size 30 an equal chance to be selected.

d. it doesn’t involve strata or clusters.

e. it is guaranteed to be representative of the population.
See all solutions

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