Validity of a new assessment rubric for a short-answer test of clinical reasoning

The validity of high-stakes decisions derived from assessment results is of primary concern to candidates and certifying institutions in the health professions. In the field of orthopaedic manual physical therapy (OMPT), there is a dearth of documented validity evidence to support the certification process particularly for short-answer tests. To address this need, we examined the internal structure of the Case History Assessment Tool (CHAT); this is a new assessment rubric developed to appraise written responses to a short-answer test of clinical reasoning in post-graduate OMPT certification in Canada.

Fourteen physical therapy students (novices) and 16 physical therapists (PT) with minimal and substantial OMPT training respectively completed a mock examination. Four pairs of examiners (n = 8) participated in appraising written responses using the CHAT. We conducted separate generalizability studies (G studies) for all participants and also by level of OMPT training. Internal consistency was calculated for test questions with more than 2 assessment items. Decision studies were also conducted to determine optimal application of the CHAT for OMPT certification.

The overall reliability of CHAT scores was found to be moderate; however, reliability estimates for the novice group suggest that the scale was incapable of accommodating for scores of novices. Internal consistency estimates indicate item redundancies for several test questions which will require further investigation.

Future validity studies should consider discriminating the clinical reasoning competence of OMPT trainees strictly at the post-graduate level. Although rater variance was low, the large variance attributed to error sources not incorporated in our G studies warrant further investigations into other threats to validity. Future examination of examiner stringency is also warranted.