An investigation into the measurement invariance of the performance index
Thesis (MComm (Industrial Psychology))--University of Stellenbosch, 2006.
The leadership-for-performance framework designed by Spangenberg and Theron (2004) aspires to explicate the structural relationships existing between leader competency potential, leadership competencies, leadership outcomes and the dimensions of organizational unit performance. The Performance Index (PI) and Leadership Behaviour Inventory (LBI) comprise the leadership-forperformance range of measures. The PI was developed as a comprehensive criterion measure of unit performance for which the unit leader could be held responsible. The basic PI structural model has been developed to explain the manner in which the various latent leadership dimensions measured by the LBI affect the eight unit performance latent variables that are assessed by the PI. Although preliminary research suggests the basic PI structural model could be refined, continued research in this regard can only be justified if the basic PI measurement model is shown to be measurement invariant across independent samples from the target population. As part of ongoing research of the leadership-for-performance range of measures, this crossvalidation study investigated the extent to which the PI measurement model may be considered measurement invariant across two independent samples from the same population. Two samples were collected through non-probability sampling procedures and included 277 and 375 complete cases after imputation by matching. Item analysis and dimensionality analysis were performed on each of the PI sub-scales prior to the formation of item parcels. No items were excluded based on item- and dimensionality analysis results. Two composite indicator variables (item parcels) were created from the items of each sub-scale and were treated as continuous variables in the subsequent statistical analyses. Structural equation modelling, using robust maximum likelihood estimation, was used to perform a confirmatory first-order factor analysis on the item parcels for each sample. The measurement model was fitted to both samples independently and close fit for each sample was established. The measurement model was cross-validated using a progressive series of measurement invariance tests. Results indicated the PI measurement model did not display full measurement invariance across the two samples although it did cross-validate successfully under the configural invariance condition. Statistically significant non-equivalence was found to exist in both the measurement error variances and the factor covariances (p<0,05), although the p<0,05 critical value was only narrowly surpassed in both cases. The measurement model did, however, display metric invariance across the samples as no significant differences were found between the factor loadings, suggesting the content of each item is perceived and interpreted in a similar manner across samples from the target population. When considered in combination, these results may be viewed as quite satisfactory as they indicate that themeasurement model does not appear to vary greatly when fitted to data from the two samples. As this study has established at least metric invariance of the PI, it therefore provides some basis of confidence for proceeding with subsequent research aimed at establishing the structural invariance of the basic PI structural model and eventually research that links the leadership behaviour to work unit performance as measured by the PI. Limitations of this study are discussed.