Chapter 9 (Internal Validity Threats & Prevention)

One-Group Pretest/Posttest Design

Also known as the 'Really Bad Experiment'; lacks comparison group

Maturation Threats

Behavior change over time; prevented by comparison group

History Threats

External event affecting treatment group; prevented by comparison group

Regression Threats

Extreme scores regress towards the mean; prevented by comparison group

Attrition Threats

Participant reduction affecting validity; prevented by analyzing dropouts

Testing Threats

Order effect from repeated testing; prevented by alternate test forms

Placebo Effects

Double-blind placebo control study to rule out effects

Ceiling Effect

Scores clustered at high end of DV

Floor Effect

Scores clustered at low end of DV

Measurement Error

Reduced by using reliable, precise measures and larger samples

Individual Differences

Variability due to unique participant traits

Situation Noise

External distractions causing variability

Power

Likelihood of study detecting real effects

Null Results Reporting

Transparent reporting of studies with no significant effects

Null Effects Publication

Increasing likelihood of journals publishing null effect research