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Criterion validity assesses how well a scale correlates with or predicts an external criterion. Let's consider a case study in the context of clinical psychology to illustrate this concept.
Case Study: Validating a New Depression Assessment Scale
In this case, researchers have developed a new self-report scale to assess the severity of depressive symptoms in clinical populations. To establish criterion validity, they must compare their new scale with a well-established criterion measure—commonly a clinical interview.
Data Collection: A group of individuals with diagnosed clinical depression is recruited for the study. They complete both the new self-report scale and a clinical interview conducted by trained clinicians.
Concurrent Validation: The researchers calculate the correlation between the scores obtained from the self-report scale and the clinical interview. A high positive correlation indicates that the new scale is concurrent with the clinical interview, providing evidence of concurrent validity.
Predictive Validation: The participants' scores on the new scale are tracked over time. Researchers then assess the degree to which scores on the initial assessment predict future clinical outcomes, such as the need for therapeutic interventions or changes in medication.
The concurrent and predictive validation methods help establish the criterion validity of the new depression assessment scale by demonstrating its ability to correlate with and predict clinical interview outcomes.
