What does internal validity primarily focus on in a study?

Internal validity primarily focuses on the control of extraneous factors within a study. It assesses whether the results of the study can be attributed to the manipulations of the independent variable rather than to other potential confounding variables. In tightly controlled experimental designs, researchers aim to eliminate or minimize the influence of external variables that could affect the outcome, thereby establishing a clearer cause-and-effect relationship.

For instance, if a study tests the effectiveness of a new treatment, high internal validity would ensure that any observed effects can be confidently linked to the treatment itself, not influenced by outside factors such as participant characteristics, environmental variables, or measurement inaccuracies. Thus, maintaining stringent control of these extraneous factors is essential for drawing valid conclusions from the study data.