Threats to internal validity

Threats to internal validity

1. History threat

2. Maturation threat

3. Testing threat

4. Instrumentation threat

5. Mortality threat

6. Regression threat

7. Selection threat

8. Social interaction threat

Threats to internal validity: History threat

A threat to internal validity that occurs when some historical event affects your study outcome

Threats to internal validity: Maturation threat

In general, if a specific event or chain of events could cause the outcome, it is a history threat, whereas a maturation threat consists of all the events that naturally occur in your life that could cause the outcome (without being specific as to which ones are the active causal agents)

Threats to internal validity: Testing threat

When taking the pretest affects how participants do on the posttest

Threats to internal validity: Instrumentation threat

When the instruments (or observers) used on the posttest and pretest differ

Threats to internal validity: Mortality threat

Significant number of participants drop out - the researcher can gauge the degree of the threat by comparing the drop-out group against the non-drop-out group on pretest measures. If there are no major differences, it may be more reasonable to assume that mortality was happening across the entire sample and is not biasing results greatly.

Threats to internal validity: Regression threat 1

A statistical phenomenon that causes a group's average performance on one measure to regress toward or appear closer to the mean than anticipated or predicted.

Threats to internal validity: Regression threat 2

Regression occurs whenever you have a nonrandom sample from a population and two measures that are imperfectly correlated. A regression threat will bias your estimate of the group's posttest performance and can lead to incorrect causal inferences.

Threats to internal validity: Selection threat

Any factor other than the program that leads to posttest differences between groups.

Threats to internal validity: Social interaction threat

Diffusion or imitation of treatment, compensatory rivalry, resentful demoralization, compensatory equalization of treatment