What does internal validity refer to in research?

Internal validity is an essential concept in research that refers to the extent to which the results of a study accurately reflect the causal relationship between the variables being studied, within the context of the sample used. It essentially measures how well the study is designed to eliminate alternative explanations for the findings, ensuring that the observed effects are truly due to the independent variable and not confounded by other factors.

When researchers achieve high internal validity, they can confidently claim that the changes in the dependent variable are attributable to the independent variable, thus affirming that the findings are "true for the sample" being investigated. This is particularly important in experimental research, where minimizing biases and controlling variables can strengthen the credibility of the results.

In contrast, external validity pertains to the generalizability of the findings beyond the sample to the larger population. Therefore, while internal validity focuses on the accuracy and reliability of the results within the sample itself, the correct affirmation here confirms that it is indeed about the data's relevance to that specific sample.