Differentiate internal validity from external validity.

• A. Internal validity concerns whether observed effects are due to the intervention; external validity concerns generalizability.
• B. Internal validity concerns generalizability; External validity concerns causality.
• C. Internal validity is about random sampling; external about data collection accuracy.
• D. Internal validity and external validity are the same.

Answer: (A)

The main idea here is that internal validity is about whether the study can show that the intervention, and only the intervention, caused the observed effect, while external validity is about whether the study’s findings would apply to other people, settings, and times. So internal validity focuses on causal conclusions within the study, and external validity centers on generalizability beyond the study sample.

Strengthening internal validity involves design choices that reduce confounding and bias, such as random assignment, control groups, blinding, and standardized procedures. Strengthening external validity involves making the sample representative, testing in different settings and times, and considering how context might influence results.

The option is the best because it correctly pairs internal validity with causality and external validity with generalizability. The other statements mix up these concepts or claim they’re the same, which doesn’t fit how these validity types differ.