Item Response Theory and Confirmatory Factor Analysis: Complementary Approaches for Scale Development

Purpose: This article demonstrates the advantages of using both confirmatory factor analysis (CFA) and item response theory (IRT) in the development and evaluation of social work scales with dichotomous or polytomous items. Social work researchers have commonly employed CFA and internal consistency reliability tests to validate scales for use in research- and evidence-based practice; IRT has been underused. We report findings from CFA and IRT analyses of a short social isolation scale for elementary school students to demonstrate that scale development and validation can benefit from complementary use of the two methods. Results provided evidence that scores from the scale are statistically sound, and each method contributed valuable information. Method: Data collected from 626 third-through fifth-grade students using the social isolation scale from the Elementary School Success Profile (ESSP) were examined with both CFA and IRT. Results: Complementary CFA and IRT results provide detailed information about item and scale performance of the social isolation scale. Discussion: Evidence-based practice requires scales with known properties; knowledge of those properties is more complete when researchers use both CFA and IRT. Conclusion: Using IRT modeling in combination with CFA can help social work researchers ensure the quality of scales they recommend to practitioners and researchers.