How is internal validity defined in experimental research?

Internal validity in experimental research refers to the extent to which an experiment accurately establishes a causal relationship between the independent and dependent variables. It is a measure of how well the study eliminates alternative explanations for the observed effects, ensuring that the changes in the dependent variable can confidently be attributed to manipulations of the independent variable.

For instance, a high level of internal validity means that the study effectively rules out biases, confounding variables, and other threats that could influence the results. This allows researchers to make strong claims about causation, as they can assert that the factors being tested are indeed the ones causing any observed changes. In essence, strong internal validity is crucial for the credibility of experimental results.

The other choices focus on different aspects of research. The first option relates to external validity, which concerns the generalizability of results beyond the specific experimental conditions. The third option addresses the reliability of measurement tools, which is important for data quality but not a direct measure of the causal claims of the experiment. Lastly, the fourth option deals with participant satisfaction, which, while relevant to the experience of participants, does not pertain to how causality is established in the study.