Threats to Internal Validity

  1. Selection Bias or Selection Threat
    When you suspect outcomes differ between groups not because of your program, but because of prior group differences, you are suspecting selection bias
  2. Selection – History Threat
    • A threat to internal validity that results from any other event that occurs between the pretest and posttest that the groups experience differently
    • Example: One group watching Sesame Street more than the other leading to better math scores rather than the math tutoring program improving the scores
  3. Selection – Maturation Threat
    A threat to internal validity that arises from any differential rates of normal growth between pretest and posttest for the groups
  4. Selection – Instrumentation Threat
    • A threat to internal validity that results from differential changes in the test used for each group from pretest to posttest
    • The test changes differently for the two groups
  5. Selection – Mortality Threat
    A threat to internal validity that arises when there is a differential nonrandom dropout between pretest and posttest
  6. Selection – Regression Threat
    • A threat to internal validity that occurs when there are different rates of regression to the mean in the two groups.
    • Example: This might happen if on group is more extreme on the pretest than the other group
  7. Social Threats
    • 1. Diffusion of treatment
    • 2. Compensatory rivalry
    • 3. Resentful demoralization "the screw you" effect
    • 4.  Compensatory equalization of treatment
  8. Diffusion of treatment
    Social threat to internal validity that occurs because a comparison group learns about the program either directly or indirectly from the program group participants.
  9. Compensatory rivalry
    • A social threat to internal validity that occurs when one group knows the program another group is getting and because of that develops a competitive attitude with the other group
    • Example: Thinking they can do better than the program group “just to show” how well they can do which could affect post-test performance and difficult to detect effects of the program itself
  10. Resentful demoralization "the screw you" effect
    A social threat to internal validity that occurs when the comparison group knows what the program group is getting and becomes discouraged or angry and just gives up
  11. Compensatory equalization of treatment
    Control group is given a program or treatment to make up for or “compensate” for the treatment the program group is getting. But may equalize the control and treatment groups on post-test performance which works against you detecting an effective program even when it does work
Author
Anonymous
ID
313359
Card Set
Threats to Internal Validity
Description
Threats to Internal Validity
Updated