SA Journal of Industrial Psychology
On-line version ISSN 0258-5200
ORIENTATION: Psychological instruments require continued refinement, updating and evaluation. RESEARCH PURPOSE: To investigate the reliability, validity and differential item functioning of the MBTI® Form M across groups in South Africa using Classical Test Theory (CTT) and Item Response 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 research paradigm. Classical test theory methods and Rasch analysis were used to evaluate the functioning of the MBTI Form M across gender and ethnic groups. A cross-sectional study was completed consisting of 10 705 South African respondents. MAIN FINDINGS: Excellent reliability was found for the instrument across groups in the sample. Good evidence for construct validity was found using exploratory factor analysis and confirmatory factor analysis. Some evidence for uniform bias was found across ethnic and gender groups and a few items reflected non-uniform DIF across gender groups only. The effect of uniform and non-uniform DIF did not appear to have major practical implications for the interpretation of the scales. PRACTICAL/MANAGERIAL IMPLICATIONS: The results provided evidence that supports the psychometric validity of the MBTI instrument in the South African context. CONTRIBUTION/VALUE-ADD: This study is the largest study to date regarding the psychometric functioning of the MBTI instrument in South Africa. It contributes to the evolution of the instrument in line with the legislative requirements concerning the use of psychometric tests in South Africa.