Which is not a direct threat to internal validity?

Which is not a direct threat to internal validity?

(a) History

(b) Testing

(c) Sampling error

(d) Differential selection

✅ Correct option: (c) Sampling error

Explanation:

Sampling error occurs when a sample does not perfectly represent the population, affecting the accuracy of generalization rather than causal interpretation. Therefore, it is related to external validity, not internal validity. History, testing, and differential selection are direct threats to internal validity because they influence whether changes in the dependent variable are caused by the independent variable. Sampling error affects representativeness, not cause-and-effect relationships.

10 Related PPSC Facts:

Sampling error affects generalization. Internal validity concerns causality. History includes external events. Testing causes learning effects. Selection bias affects group equivalence. Randomization reduces selection threats. Larger samples reduce sampling error. Sampling error is unavoidable. Confidence intervals reflect sampling error. External validity involves sampling.