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Chapter 4: Q. R4.7 (page 288)

A recent study of 1000students at the University of Michigan investigated how to prevent catching the common cold. The students were randomly assigned to three different cold prevention methods for 6weeks. Some wore masks, some wore masks and used hand sanitizer, and others took no precautions. The two groups who used masks reported 10-50%fewer cold symptoms than those who did not wear a mask.

a. Does this study allow for inference about a population? Explain your answer.

b. Does this study allow for inference about cause and effect? Explain your answer.

Short Answer

Expert verified

a. This study does not allow for inference about a population because the students were not randomly selected from a larger population.

b. Yes.

Step by step solution

01

Part a. Step 1. Explanation

This study does not allow for inference about a population because the students were not randomly selected from a larger population.

02

Part b. Step 1. Explanation

This study allow for inference about cause and effect since treatments are assigned to the students, the study was an experiment and experiments allow for inference about cause and effect when the subjects were randomly assigned to the treatment groups and when there was a control group.

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Most popular questions from this chapter

Weekend birthdays Over the years, the percentage of births that are planned cesarean

sections has been rising. Because doctors can schedule these deliveries, there might be

more children born during the week and fewer born on the weekend than if births were

uniformly distributed throughout the week. To investigate, Mrs. McDonald and her class

selected an SRS of 73people born since1993 . Of these people, 24were born on Friday,

Saturday, or Sunday. To determine if these data provide convincing evidence that fewer than43%37 of people born since 1993were born on Friday, Saturday, or Sunday, 100simulated SRSs were selected. Each dot in the graph shows the number of people that were born on Friday, Saturday, or Sunday in a simulated SRS of 73people, assuming that each person

had a 43%chance of being born on one of these three days.

a. Explain how the graph illustrates the concept of sampling variability.

b. Based on the data from the study and the results of the simulation, is there convincing

evidence that fewer than 43%of people born since 1993were born on Friday, Saturday,

or Sunday? Explain your answer.

Can a vegetarian or low-salt diet reduce blood pressure? Men with high blood pressure are

assigned at random to one of four diets: (1) normal diet with unrestricted salt; (2)

vegetarian with unrestricted salt; (3) normal with restricted salt; and (4) vegetarian with

restricted salt. This experiment has

  1. one factor, the type of diet.
  2. two factors, high blood pressure and type of diet.
  3. two factors, normal/vegetarian diet and unrestricted/restricted salt.
  4. three factors, men, high blood pressure, and type of diet.
  5. four factors, the four diets being compared.

Bias in a sampling method is

a. any difference between the sample result and the truth about the population.

b. the difference between the sample result and the truth about the population due to

using chance to select a sample.

c. any difference between the sample result and the truth about the population due to

practical difficulties such as contacting the subjects selected.

d. any difference between the sample result and the truth about the population that

tends to occur in the same direction whenever you use this sampling method.

e. racism or sexism on the part of those who take the sample.

A gardener wants to try different combinations of fertilizer (none, 1cup, 2cups) and mulch (none, wood chips, pine needles, plastic) to determine which combination produces the highest yield for a variety of green beans. He has 60green-bean plants to use in the experiment. If he wants an equal number of plants to be assigned to each treatment, how many plants will be assigned to each treatment?

a. 1

b. 3

c. 4

d. 5

e.12

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.
See all solutions

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