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Rasch analysis on OSCE data : An illustrative example
1School of Medicine, The University of Notre Dame Australia, Fremantle.
The Australasian Medical Journal
|February 7, 2013
Summary
The polytomous Rasch model effectively evaluates the psychometric properties of Objective Structured Clinical Examination (OSCE) scores. This analysis confirms OSCE stations measure clinical competence and offers insights beyond traditional methods.
Area of Science:
- Medical Education
- Psychometrics
- Health Professions Education
Background:
- Objective Structured Clinical Examination (OSCE) is a standard for assessing clinical competence in health professions.
- OSCEs aim for reproducible pass/fail decisions and competence level assessments.
- Evaluating the psychometric properties of OSCE scores is crucial for reliable assessment.
Purpose of the Study:
- To explore the application of the polytomous Rasch model for evaluating OSCE psychometric properties.
- To determine if OSCE stations assess a common construct of clinical competence.
- To identify additional insights from Rasch analysis compared to classical test theory.
Main Methods:
- Analysis of an 11-station OSCE dataset from 80 fourth-year medical students.
- Application of the polytomous Rasch model.
- Comparison of Rasch analysis findings with classical test theory.
Main Results:
- The OSCE data demonstrated good fit to the Rasch model (p=0.76), supporting unidimensionality for clinical competence.
- Individual station scores showed good fit, reinforcing the construct validity.
- A Person Separation Index (PSI) of 0.704 indicated sufficient reliability for the OSCE scores.
Conclusions:
- The polytomous Rasch model offers a valuable supplementary method for analyzing OSCE data.
- Rasch analysis provides deeper insights into psychometric properties and instrument validation.
- This approach enhances the rigor of clinical competence assessment in health professions education.
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