External validity primarily depends on what factor?

External validity refers to the extent to which the results of a study can be generalized beyond the specific conditions or participants involved in the research. It primarily depends on the representativeness of the sample and setting. When a sample is representative of the larger population, and when the setting mimics real-world contexts, the findings are more likely to be applicable to broader situations.

For instance, if a study uses a sample that closely reflects the demographics, characteristics, and behaviors of the general population, the outcomes are more readily generalizable. Similarly, when the research setting mirrors real-world environments where the intervention or treatment would occur, it enhances the external validity. This means that practitioners can be more confident in applying the study's findings to their practice or other contexts.

In contrast, while factors like the size of the sample, the number of variables measured, and the specific research methodology employed are important for various aspects of research quality—such as internal validity, reliability, and statistical power—these elements do not inherently guarantee that the findings will be generalizable to different populations or settings. Thus, the focus on representativeness of the sample and setting directly ties to the fundamental aim of external validity.