How Many Grades of Response Categories Does the Commitment to the Profession of Medicine Scale Provide the Most Information?

In the present study, we examined the psychometric properties of the data obtained from the Commitment to Profession of Medicine Scale (CPMS) with 4-point, 5-point, 6-point, and 7-point response sets based on Item Response Theory (IRT). A total of 2150 medical students from 16 different universities participated in the study. The participants were divided into four groups consisting of 560, 544, 502, and 544 medical students. The first group (n=560) was assigned four-point, the second group (n=544) five-point, the third group (n=502) six-point, and the fourth group (n=544) seven-point Likert forms. We used R statistical software to analyze the data. The results of item calibrations conducted with the Graded Response Model (GRM) were analyzed. The results show that the eigenvalue increased from 4-point to 7-point. Similarly, the explained variance percentage and the scale's reliability increased gradually from 4-point to 7-point. The explained variance, reliability level, and eigenvalue were very close in the 5-point and 6-point forms.