Sexual Aggression and Victimization Among Adolescents in School: Using a MixIRT Analysis to Examine Measurement Equivalence

Abstract

Studies examining the frequency of sexual aggression and victimization in schools have compared different groups of respondents based on age, gender, or involvement in other types of school aggression. Between-group comparisons assume measurement equality. We examine this assumption of measurement equality using a MixIRT analysis, which combines a latent profile analysis with a Rating Scale Model Item Response Theory analysis to determine whether sexual aggressors and victims can be divided into latent classes and whether the latent traits of sexual aggression or victimization have configural, metric and scalar equivalence and through an examination of differential item functioning (DIF). This is a secondary analysis of 3746 Israeli adolescents responding to a self-report questionnaire regarding sexual aggression and victimization. Data analyses proceeded in five steps, and the unit of analysis was each respondent's responses to the aggressor and victim scales. We conducted a series of exploratory and confirmatory analyses of the aggression/victimization scale to examine configural equivalence, followed by a series of Latent Profile Analyses to determine metric and scalar equivalence. Finally, we examined DIF and Wright Maps using a Rating Scale IRT model. Four latent classes were identified. All items showed configural equivalence and most exhibited metric and scalar equivalence. An examination of DIF and Wright Maps showed that the structures of the latent traits for each latent class were fairly similar. However, for all latent classes, measures of sexual aggression and victimization failed to sample the full range of item difficulty (or endorseability).

Keywords: MixIRT; latent profile analysis; peer aggression; school aggression; sexual aggression; sexual victimization.

Figure 1

Class solutions. A, aggressor; V, victim. Numbers in parentheses are item numbers (see Appendix). [Color figure can be viewed at wileyonlinelibrary.com]

Figure 2

DIF by latent response class. Horizontal dashed lines mark upper and lower boundaries of acceptable DIF, no DIF if t > |1.96 |. A, aggressor; V, victim. Numbers in parentheses are item numbers (see Appendix). [Color figure can be viewed at wileyonlinelibrary.com]

Figure 3

Wright Map for sexual aggression/victimization scales, A, aggressor; V, victim, N = 3376. Aggression items are bolded, and victim items are underlined to facilitate reading. Circled items have problematic measurement equivalence.