What does it mean for an evaluation to be 'valid'? A critical synthesis of evaluation literature

Validity is both a critical foundation for, and widely contested concept in the field of program evaluation. Given the wide and divergent treatment of the term, this article sought to enhance the field's understanding and application of validity by systematically identifying, collating and integrating existing conceptions of validity. A critical interpretive synthesis approach was taken to combine the best elements of systematic literature searching with integrative review. We found that conceptions of validity could be roughly collated into three categories pertaining to the evaluation research, evaluative judgement and reporting, and beyond the evaluation proper. The result was a wide-ranging map of validity concepts against the various stages of the evaluation process. This made clear several gaps in the validity thinking, resulting in the development of comprehensive but not yet complete framework that weaves together related aspects identified into a cohesive whole. It is our hope that this initial iteration of a cohesive validity framework will be the starting point for a cooperative effort to improve professional evaluation practice.