You conduct a study on a group of individuals to examine the role of exercise on depression alleviation. You assign the first 50 people who are motivated to sign up to the experimental group, and the second group of 50 people, who sign up much later, to the control group. After one month, you find that the experimental group (who exercised three times a week on average) is significantly less depressed than the control group (who exercised one time a week on average). Although you may be tempted to conclude that exercise helps stave off depression, you cannot because of a lack of _____ in your study.
A) random sampling
B) random assignment
C) random surveying
D) random control

Question

Quizplus · Accepted Answer

The best choice is random assignment, as it would help ensure that the groups are equivalent and any differences can be attributed to the independent variable (exercise). Without random assignment, there may be other factors influencing the results, such as individual differences in motivation or severity of depression. Random sampling, random surveying, and random control are not directly relevant to the issue at hand.

You Conduct a Study on a Group of Individuals to Examine