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Chapter 4: Q. T4.9 (page 290)

You wonder if TV ads are more effective when they are longer or repeated more often

or both. So you design an experiment. You prepare 30-second and 60-second ads for a

camera. Your subjects all watch the same TV program, but you assign them at random

to four groups. One group sees the 30-second ad once during the program; another sees

it three times; the third group sees the 60-second ad once; and the last group sees the

60-second ad three times. You ask all subjects how likely they are to buy the camera.

Which of the following best describes the design of this experiment?

a. This is a randomized block design, but not a matched pairs design.

b. This is a matched pairs design.

c. This is a completely randomized design with one explanatory variable (factor).

d. This is a completely randomized design with two explanatory variables (factors).

e. This is a completely randomized design with four explanatory variables (factors).

Short Answer

Expert verified

The correct option is:

d. This is a completely randomized design with two explanatory variables (factors).

Step by step solution

01

Given information

We have been given four options from which we have to select the correct one.

a. This is a randomized block design, but not a matched pairs design.

b. This is a matched pairs design.

c. This is a completely randomized design with one explanatory variable (factor).

d. This is a completely randomized design with two explanatory variables (factors).

e. This is a completely randomized design with four explanatory variables (factors).

02

Explanation

It is a perfectly randomised design because all individuals were randomly assigned to one of the four groups.This is a completely randomized design with two explanatory variables (factors).

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Most popular questions from this chapter

Explain it to the congresswoman You are on the staff of a member of Congress who is considering a bill that would provide government-sponsored insurance for nursing-home care. You report that 1128 letters have been received on the issue, of which 871 oppose the legislation. “I’m surprised that most of my constituents oppose the bill. I thought it would be quite popular,” says the congresswoman. Are you convinced that a majority of the voters oppose the bill? How would you explain the statistical issue to the congresswoman?

Consider an experiment to investigate the effectiveness of different insecticides in

controlling pests and their impact on the productivity of tomato plants. What is the best

reason for randomly assigning treatment levels (spraying or not spraying) to the

experimental units (farms)?

a. Random assignment eliminates the effects of other variables, like soil fertility.

b. Random assignment eliminates chance variation in the responses.

c. Random assignment allows researchers to generalize conclusions about the

effectiveness of the insecticides to all farms.

d. Random assignment will tend to average out all other uncontrolled factors such as

soil fertility so that they are not confounded with the treatment effects.

e. Random assignment helps avoid bias due to the placebo effect.

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

No tipping The owner of a large restaurant is considering a new "no tipping" policy and wants to survey a sample of employees. The policy would add 20% to the cost of food and beverages and the additional revenue would be distributed equally among servers and kitchen staff. Describe how to select a stratified random sample of approximately 30 employees. Explain your choice of strata and why stratified random sampling might be preferred in this context.

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.
See all solutions

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