Chapter 9, Internal Validity Video Solutions, Research Design Explained

Problem 1

What questions would you ask a researcher who said that the no-treatment and treatment groups were identical before the start of the study?

Aditya Sood

Numerade Educator

02:12

In all of the following cases, the researcher wants to make cause-effect statements. What threats to internal validity is the researcher apparently overlooking?
a. Employees are interviewed on job satisfaction. Bosses undergo a 3-week training program. When employees are reinterviewed, dissatisfaction seems to be even higher. Therefore, the researcher concludes that the training program caused further employee dissatisfaction.
b. After completing a voluntary workshop on improving the company's image, workers are surveyed. Those who attended the workshop are now more committed than those in the no-
treatment group who did not make the workshop. Therefore, the researcher concludes that the workshop made workers more committed.
c. After a 6-month training program, employee productivity improves. Therefore, the researcher concludes that the training program caused increased productivity.
d. Morale is at an all-time low. As a result, the company hires a "humor consultant." A month later, workers are surveyed and morale has improved.
Therefore, the researcher concludes that the consultant improved morale.
e. Two groups of workers are matched on commitment to the company. One group is asked to attend a 2-week workshop on improving the company's image; the other is the no-treatment group. Workers who complete the workshop are more committed than those in the notreatment group. Therefore, the researcher concludes that the workshop made workers more committed.

Nick Johnson

Numerade Educator

02:39

Problem 3

A hypnotist claims that hypnosis can cause increases in strength. To "prove" this claim, the hypnotist has participants see how many times they can squeeze a hand-grip in 2 minutes. Then, he hypnotizes them and has them practice for 2 weeks. At the end of 2 weeks, they can squeeze the hand-grips together many more times than they could at the beginning. Other than hypnosis, what could have caused this effect?

Lucas Finney

Numerade Educator

Problem 4

How could a quack psychologist or "healthcare expert" take advantage of regression toward the mean to make it appear that certain phony treatments actually worked? Why should a baseball team's general manager consider regression toward the mean when considering a trade for a player who made the All-Star team last season?

Check back soon!

01:20

Problem 5

How could a participant's score on an ability test change even though the person's actual ability had not?

John Wells

Numerade Educator

03:08

Problem 6

Suppose a memory researcher administers a memory test to a group of residents at a
nursing home. He finds grade-school students who score the same as the older patients on the memory pretest. He then administers an experimental memory drug to the older patients. A year later, he gives both groups a posttest.
a. If the researcher finds that the older patients now have a worse memory than the grade-school students, what can the researcher conclude? Why?
b. If the researcher finds that the older patients now have a better memory than the grade-school students, what can the researcher conclude? Why?

James Kiss

Numerade Educator

01:08

Problem 7

Suppose there is a correlation between the use of night-lights in an infant's room an increased incidence of nearsightedness later. What might account for this relationship?

Averell Hause

Carnegie Mellon University

01:21

Problem 8

What is the difference between a. testing and instrumentation? b. history and maturation?

Harsh Gadhiya

Numerade Educator

02:36

Problem 9

Suppose a researcher reports that a certain argument strategy has an effect, but only on those participants who hold extreme attitudes. Why might the researcher be mistaken about the effects of the persuasive strategy?