Internal validity concerns which of the following?

• A. The extent to which observed effects are due to the manipulation of the independent variable
• B. The consistency of results across items
• C. The generalizability to other settings or populations
• D. The accuracy of the measurement

Answer: (A)

Internal validity is about whether we can attribute observed changes in the dependent variable to the experimental manipulation of the independent variable, rather than to other, alternative factors. It’s the confidence that the study’s design controls for confounds and biases—through random assignment, proper control groups, standardized procedures, and careful measurement—so the cause-and-effect link is credible within the study.

This is why the best choice emphasizes that the observed effect arises from the manipulation itself. The other ideas point to different concerns: generalizability to other settings or populations relates to external validity; consistency across items speaks to reliability; and the accuracy of the measurement touches on measurement validity or quality, not the causal inference within the study.