Reactive effects to evaluation. Simple awareness by clients that they are in a study could lead to changes in client performance. Example: All employees at a public agency providing services to the...

Reactive effects to evaluation. Simple awareness by clients that they are in a study could lead to changes in client performance. Example: All employees at a public agency providing services to the elderly were participants in a study comparing their work with work performed by practitioners in a private agency. Knowing they were in the study, and knowing they had to do their best, the public agency practitioners put in extra time, clouding the issue as to whether their typical intervention efforts would produce similar results.