Practice question
Experimental Design

Identify threats to internal validity in weak designs.

Original BCBA scenario practice question with answer explanation and wrong-choice notes.

Question

Difficulty: medium. Skill: apply. Type: experimental design critique.

interrupting peers decreases after an intervention in a simple AB design, but a new staff routine in the elementary classroom also began that same week. What is the main concern? The case is being discussed after two weeks of stable attendance.

A
A confounding variable limits confidence that the intervention caused the change

Correct answer

B
The aide proves the intervention was unnecessary
C
The decrease should be ignored because all AB designs are invalid
D
Internal validity is unrelated to treatment evaluation

Explanation

Answer A

A concurrent change can threaten internal validity because it competes with the intervention as an explanation for behavior change.

Why the other choices are weaker

B
Choice B

The aide is a possible confound, not proof of the true cause.

C
Choice C

AB data can be useful clinically, but causal confidence is limited.

D
Choice D

Internal validity concerns whether the intervention caused the observed change.

Study tags

Internal ValidityExperimental ControlChanging Criterion

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