What does high internal validity allow researchers to confidently establish?

High internal validity is crucial for establishing a cause-and-effect relationship between variables in a study. When a study has high internal validity, it means that the researchers have minimized potential confounding variables and biases, allowing them to confidently assert that changes in the independent variable directly lead to changes in the dependent variable. This is important because it strengthens the argument that the relationship observed is not influenced by external factors, thereby confirming causation rather than mere correlation.

In this context, the presence of a control group is useful for high internal validity, but it does not inherently establish causal relationships on its own. Similarly, generalizability of results (external validity) and representativeness of the sample pertain more to how the findings can be applied to a larger population, which is distinct from the concept of establishing causation. High internal validity focuses primarily on the integrity of the experimental design and the confidence in the cause-and-effect conclusions drawn from the data collected.