Original Research

Over reliance on model fit indices in confirmatory factor analyses may lead to incorrect inferences about bifactor models: A cautionary note

Tyrone B. Pretorius
African Journal of Psychological Assessment | Vol 3 | a35 | DOI: https://doi.org/10.4102/ajopa.v3i0.35 | © 2021 Tyrone B. Pretorius | This work is licensed under CC Attribution 4.0
Submitted: 29 September 2020 | Published: 12 March 2021

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Tyrone B. Pretorius, Department of Psychology, Faculty of Community and Health Sciences, University of the Western Cape, Cape Town, South Africa

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This brief article attempts to describe the importance of relying not just on model fit indices, but also on bifactor, confirmatory factor analysis to examine the factor structure of instruments presumed to be multidimensional. Three ancillary bifactor indices (explained common variance, omega hierarchical and percentage uncontaminated correlations) were calculated for three instruments that have been described as multidimensional in published research. One of these instruments, the Normative Beliefs about Aggression Scale (NOBAGS) demonstrated strong evidence of multidimensionality. The second instrument, Problem-Solving Inventory demonstrated some evidence of multidimensionality, but must be considered essentially unidimensional because of lack of sufficient evidence. The third instrument, Cyberchondria Severity Scale demonstrated essential unidimensionality with little evidence of multidimensionality. These findings support the argument that using only model fit statistics may lead researchers to draw incorrect conclusions about the dimensionality of an instrument.


ancillary bifactor indices; bifactor models; model-fit indices; multidimensionality; unidimensionality


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