Equivalence of psychological measurement in heterogeneous populations
A method for investigating measurement equivalence across subpopulations is developed and applied to an instrument frequently used to assess job satisfaction (the Job Descriptive Index; JDI). The method is based on Jöreskog’s simultaneous factor analysis in several populations. Several adaptations are necessary to overcome problems with violations of assumptions that occur with rating scale data. Two studies were conducted to evaluate the measurement equivalence of the JDI across different subpopulations. Investigation of five relatively homogeneous subpopulations within one industry revealed invariant measurement properties for the JDI. In the second study, measurement equivalence of the JDI was examined across health care, retailing, and military samples. Generally small violations of measurement equivalence were found. The results in both studies indicate that mean differences in JDI scores (i.e., differences in job satisfaction across groups) are due to group differences rather than lack of measurement equivalence.