The Nursing Student Self-Efficacy Scale: development using item response theory.

BACKGROUND: For nurse educators to optimize instruction that supports students' accurate estimates of their ability, a sound measure of nursing self-efficacy is needed.
OBJECTIVE: To provide evidence for an adequate item response theory model fit to scores measuring nursing students' self-efficacy to care for critically ill patients and to use the theory to provide evidence for reliable and valid interpretation of self-efficacy scores.
METHODS: The Nursing Student Self-Efficacy Scale was administered to 421 nursing students. Data regarding students' self-efficacy beliefs for psychomotor skill performance and communication skills were analyzed using the generalized partial credit item response theory model.
RESULTS: All items showed acceptable model-data fit using the chi-square test with an alpha of .001. Review of item information functions showed that 40% of the items provided high information about self-efficacy and 20% provided moderately high information. Comparison of trait level distributions with reliability information given by the two subscales showed that the psychomotor subscale measured self-efficacy most accurately for second and third semester students and the communication subscale measured efficacy most accurately for first and second semester students. Significant mean differences in self-efficacy scores from both subscales were found between students in successive semesters of the program. DISCUSSION: Data analysis provided some evidence for reliable interpretation of scores indicating self-efficacy beliefs of nursing students. Comparison of scores from students in different semesters provided validity evidence; the instrument could be used to discriminate between beginning students and more advanced students possessing different levels of self-efficacy. When used for scale development, item response theory procedures can be more informative about item and test reliability than classical true score theory.