Pre, Quasi, and Exp Designs, and, Internal and External Validity

Question 1

List all threats to internal validity.

Answer 1

CATCH DIRT MUD. compensatory rivalry, attrition, treatment diffusion, compensatory equalization, history, demoralization, instrumentation (it changed), regression to the mean, testing, maturation, unstable instrumentation (unreliable instrument), differential selection

Question 2

What is the definition of a threat to external validity?

Answer 2

The degree that the research sample does not adequately represent the target population.

Question 3

What are the threats to external validity?

Answer 3

TEES. testing (experimental outcomes are sensitive to the use of particular instruments), effects of prior treatment (if a treatment is administered prior to the treatment of interest then effects may result from lagged prior treatment effects), experimental artificiality (unrealistic conditions experienced during experiment), “selection bias” (unrepresentative sample).