An Item Response Theory Analysis of the Strength and Difficulties Questionnaire (SDQ)

Abstract

Abstract. The Strengths and Difficulties Questionnaire (SDQ) assesses five subscales for measuring child adjustment. In the present study, an item response theory approach was used to analyze the parent version of the SDQ subscales and the total difficulties score (TDS), which is obtained by summing up the scores of the four problem subscales. Analyses are based on two data sets: The German Family Panel “Panel Analysis of Intimate Relationships and Family Dynamics (pairfam, N = 1,078)” and the survey “Growing up in Germany” (Aufwachsen in Deutschland: Alltagswelten; AID:A, N = 1,346). Partial credit and generalized partial credit models were estimated for each subscale and a bifactor model was applied to the TDS. The results showed satisfying psychometric properties in both samples for each of the five subscales, except for the “Hyperactivity/Inattention” subscales which seemed to have a two-dimensional structure. Item discrimination and category threshold parameters were broadly comparable between the samples. According to the bifactor models, there is evidence for multidimensionality in the TDS, but the general factor was strong. Thus, the TDS can be treated as essentially unidimensional, although some subscales may be of additional value.