Rasch analysis of the International Personality Item Pool Big Five Markers Questionnaire: Is longer better?

Abstract

The 50-item International Personality Item Pool version of the Big Five Markers (IPIP-BFM) is an open-source and widely used measure of the big five personality traits. A short version of this measure (IPIP-BFM-25) has been developed using the classical test theory approach. No study was performed to examine the psychometric properties of a longer and shorter version of IPIP-BFM Indonesia using modern test theory. This study aimed to evaluate the psychometric properties of the Indonesian version of IPIP-BFM as well as IPIP-BFM-25 using Rasch analysis. The analysis was conducted in order to test their dimensionality, rating scale functioning, item properties, person responses, targeting, reliability, and item bias on 1003 Indonesian samples. The findings showed that both IPIP-BFM and IPIP-BFM-25 Indonesia have some adequate psychometric properties, especially regarding category function, item properties, reliability, and item bias. However, the emotional stability and intellect scales did not meet the assumption of unidimensionality, and all items on the scales were too easy to endorse by participants. In general, longer measures outperformed shorter measures in terms of person separation and reliability. Further testing and refinement must be conducted.