The Parent Version of the Strengths and Difficulties Questionnaire Omega as an Alternative to Alpha and a Test for Measurement Invariance

The Strengths and Difficulties Questionnaire (SDQ) is a widely used screening instrument for child psychopathology. Many studies have consistently reported rather low alpha values for certain subscales for the SDQ parent version. Further, the factor structure has not been tested frequently by using confirmatory factor analysis (CFA); research into measurement invariance is even scarcer. Therefore, this study evaluates the internal reliability and tests for measurement invariance for the SDQ parent version. In a Dutch sample of 1,484 children we examined reliability by using coefficient omega and tested for invariance across several subgroups. Also, we conducted CFA to examine the five-factor structure of the SDQ. omega yielded higher values than alpha did, which supports the use of omega in a SEM-based framework. Support for measurement invariance was found on the configural, metric, and scalar level, and as expected, the five-factor structure was confirmed. Scholars are advised to consider omega as an alternative to alpha, seeing that various problems with alpha have been discussed. Support for measurement invariance was found for several demographic variables, so that meaningful group comparisons can now be made for the SDQ parent version.