What is internal validity?

Internal validity refers to the degree to which a study accurately reflects the true causal relationship between the intervention and the observed outcomes, free from the influence of confounding variables. It focuses on ensuring that the results are attributable to the experimental conditions and not other factors. High internal validity indicates that the study design, conduct, and analysis effectively eliminate or control for biases and confounding variables that could distort the results.

In contrast, the other options discuss different aspects of research or validity. The option regarding generalizability pertains to external validity, which assesses how applicable findings are to other settings or populations. The choice that mentions a type of observational study refers to study design rather than validity. The measure of practical significance relates to the clinical relevance of results, rather than the integrity of the causal relationships established within the study. Thus, the focus of internal validity is squarely on the accuracy of causal inferences derived from the study.