Exam 9: Internal Validity

Explain why matching is not a perfect way of making two groups equal.

If you don't realize that scores may be affected by random error, you may fail to detect ____ effects.

Participants who scored very low on a test, will tend to score ____ on the retest:

Why might participants' scores change between pretest and posttest?

The fact that participants are not matched on every single variable makes matching most vulnerable to:

Give an example of regression affecting the results of a two group study. Then, give an example of regression affecting the results of a pretest/posttest study.

The goals of internal and external validity

The pretest-posttest design is an imperfect substitute for random assignment to condition.

Shortly after seeing a quack, several people have recovered from an illness, regaining their former health. The best explanation for their recovery is

Matching is the best way of making sure that your groups are equivalent before the treatment is administered.

When trying to establish that a treatment causes an effect, researchers ALWAYS try to

List, define, and give an example of each of Campbell and Stanley's threats to validity.

In order to be confident that your treatment caused an observed effect, you must establish that the study has internal validity.