One of the dirty little secrets in the assessment business is the way that assessments are validated. There are no formal systematic approaches for the validation of tests that are easy for tests users, not versed in statistics, to follow.
Instead of asking about validity, the real question should be “How useful is this assessment or intervention?” This leads to the more focused question of how useful this assessment or intervention is for the problem.
The Myth That Criterion Related Validity Is a Simple Correlation Between Test Score and Work Outcome
Criterion validity is far more than the simple correlations that are found in technical manuals. Validity in this sense is more appropriately described as whether an assessment can deliver a proposed outcome in a given setting with a given group.