Adjustment for guessing in a basic statistics test for Indonesian undergraduate psychology students using the rasch model

Abstract

The purpose of this study comprises (1) calibrating the Basic Statistics Test for Indonesian undergraduate psychology students using the Rasch model, (2) testing the impact of adjustment for guessing on item parameters, person parameters, test reliability, and distribution of item difficulty and person ability, and (3) comparing person scores after adjustment for guessing with original analysis results. Adjustment for guessing was performed using the Rasch model-based method with a tailored analysis. Participants were 488 undergraduate psychology students (221 male, 267 female; mean age = 18.86, SD = 0.49) in Indonesia. The Rasch analysis results show that the assumptions of unidimensionality and local independence of the Basic Statistics Test are met. However, the two items do not fit the Rasch model on the original or tailored analysis. Comparing the original and tailored analyses shows that adjustment for guessing impacts the item parameters, person parameters, reliability, and distribution of item difficulties and person abilities. With the university’s minimum pass-levels (MPL) based on total scores (scores > 60), adjustment for guessing resulted in more respondents passing the MPL. Thus, adjustment for guessing is recommended for making pass-fail decisions based on a predetermined MPL. Implications and suggestions for future research are discussed.