Internal validity, as defined by Campbell and Stanley, is a logical rather than statistical issue. Statistical tests establish the likelihood that the study results are due to chance variation ...

Internal validity relates to the way a test is performed, while external validity examines how well the findings may apply in other settings. Criterion-Related Validity.

The upshot is that without internal validity, you can’t draw scientific conclusions. But without external validity, you have nothing worth drawing conclusions about.

Internal validity Assess internal validity on basis of research design and operational procedures. Difference is most likely due to the treatment; proceed to next step.

Internal validity is scientific validity. The extent to which a researcher devises a solid experiment, controls for confounding variables, and executes the procedure as planned determines a ...