Evaluating the MBTI Form M in a South African context

Orientation: Psychological instruments require continued refinement, updating andevaluation.Research purpose: To investigate the reliability, validity and differential item functioning ofthe MBTI Form M across groups in South Africa using Classical Test Theory (CTT) and ItemResponse Theory (IRT) methods.Motivation for the study: To add to the continual research and improvement of the MBTI Form M through the investigation of its psychometric properties across groups in South Africa.Research design, approach and method: This study falls within the quantitative researchparadigm. Classical test theory methods and Rasch analysis were used to evaluate thefunctioning of the MBTI Form M across gender and ethnic groups. A cross-sectional study wascompleted consisting of 10 705 South African respondents.Main findings: Excellent reliability was found for the instrument across groups in thesample. Good evidence for construct validity was found using exploratory factor analysis andconfirmatory factor analysis. Some evidence for uniform bias was found across ethnic andgender groups and a few items reflected non-uniform DIF across gender groups only. Theeffect of uniform and non-uniform DIF did not appear to have major practical implications forthe interpretation of the scales.Practical/managerial implications: The results provided evidence that supports thepsychometric validity of the MBTI instrument in the South African context.Contribution/value-add: This study is the largest study to date regarding the psychometricfunctioning of the MBTI instrument in South Africa. It contributes to the evolution of theinstrument in line