Key Issues

In this chapter, we address eight questions:

1. What three criteria must be met to establish that one factor causes a certain effect?

2. How does the simple experiment establish internal validity?

3. What are the two errors that can result from a statistical test?

4. How do statistical considerations affect the design of the simple experiment in terms of

a. The way participants are assigned to group,

b. The degree to which participants are allowed to interact,

c. Whether participants are run in groups,

d. The number of participants in the study,

e. The strength of the manipulation, and

f. The measure used.

5. How might statistical considerations conflict with other goals, such as the goals of having construct validity, of having external validity, and of being ethical?

6. What does the top of the t-ratio represent? What does the bottom of the t-ratio represent?

7. What questions are raised by null results?

8. What questions should be asked about significant results from a simple experiment?