A study's results are due to the independent variable rather than to confounds.

internal validity

Explanation:

Internal validity is a method of measuring how accurate a research is. It seeks to validate your research based on how well it was done regarding the influence of confounding variables in your experiment. If experiment is run and confounding variables are avoided, your internal validity will be high and the more confounding variables you have, the lower your internal validity. This would however mean that your experiment was influenced by just one independent variable and thereby validate it's accuracy.