Development of an instrument for measuring self-efficacy in cell biology

This article describes the development of a ten-item scale to assess biology majors' self-efficacy towards the critical thinking and data analysis skills taught in an upper-division cell biology course. The original seven-item scale was expanded to include three additional items based on the results of item analysis. Evidence of reliability and validity was collected and reported for the revised scale. In addition, the effect of varying the number of response categories presented with the items was empirically examined by administering different versions of the instrument containing 6, 11, 21, and 101 response categories to randomly selected samples of students in the course. Rasch scaling procedures were used to analyze the results. Contrary to Bandura's recommendation for using the 101-point scale (0-100), the results indicated that most respondents used only a subset of the options in the 101-point scale and that the 6-point and 11-point scales produced less threshold disordering for the purpose of assessing changes in students' self-efficacy in the context of a one-semester course.