Experimental Design
Internal validity and confounds
Evaluate whether behavior change can be attributed to the intervention or whether other concurrent changes compete as explanations.
How this shows up in scenario questions
- 1Identify concurrent staff or setting changes as confounds.
- 2Explain why replication strengthens causal confidence.
- 3Recognize limits of AB designs.
Common misconceptions
- Assuming any pre-post improvement proves intervention effect.
- Ignoring concurrent changes.
- Treating clinical usefulness as experimental control.
Distractor patterns
- Declare the intervention causal without replication.
- Dismiss all AB data as useless.
- Ignore treatment integrity and setting changes.
Related terms
confounding variablesexperimental controlthreats to validity
Related practice prompts
Identify threats to internal validity in weak designs.
repeating questions decreases after an intervention in a simple AB design, but a new staff routine in the early-intervention session also began that same week. What is the main concern? The program is being updated before services move to a new setting.
Identify threats to internal validity in weak designs.
throwing materials decreases after an intervention in a simple AB design, but a new staff routine in the clinic session also began that same week. What is the main concern? The case is being discussed after two weeks of stable attendance.
Identify threats to internal validity in weak designs.
screaming decreases after an intervention in a simple AB design, but a new staff routine in the vocational training room also began that same week. What is the main concern? The BCBA is reviewing the decision with a trainee.