Is Less More? Reevaluating the Psychometric Properties of the Sense of Coherence-13 and a Revised Seven-Item Version in South Africa Using Classical Theory and Item Response Theory

Abstract

Studies on the dimensionality and factor structure of the Sense of Coherence-13 (SOC-13) scale have produced inconsistent results, and there is a need for comprehensive psychometric testing of the scale in different populations and using diverse methodologies. SOC refers to the individual’s ability to perceive life as comprehensible, manageable, and meaningful. The current study investigated the dimensionality of the SOC-13 through the use of confirmatory factor analysis (CFA), ancillary bifactor indices and item response theory in a sample of young adults in South Africa. Participants were students (n = 322) who completed the SOC-13, the Connor–Davidson Resilience Scale, the PTSD Checklist for DSM-5 and short forms of the Center for Epidemiological Studies Depression Scale, and the trait scale of the Spielberger State-Trait Anxiety Inventory. CFA indicated the best fit for a one-factor model, but the problematic parameter estimates raise concerns about the construct validity of the scale. Non-parametric item response theory (Mokken scale analysis [MSA]) identified limitations in the original 13-item version, suggesting a more dependable seven-item version (SOC-7). This revised scale exhibited strong psychometric characteristics and was consistent with the theoretical foundations that underpin the construct. We verified the unidimensional structure of the SOC with the more stringent parametric item-response theory (Rasch analysis) which confirmed that the seven-item SOC is unidimensional. Rasch analysis confirmed the measurement invariance of the SOC-13 in terms of gender and area of residence. The study suggests that a shorter seven-item version consisting of items from the three components of sense of coherence has comparative properties to the 13-item version but the evidence does not provide support for the use of the SOC-13 as a multidimensional measure. Research in the area of sense of coherence would benefit from further validation studies of both the original SOC-13 and the revised SOC-7, especially across populations and settings.