Rape Myth Acceptance Scale: An Item Response Theory Analysis

Background: Self-report surveys revealed that approximately 2.5% of women in England and Wales have been a victim of a sexual violence in the previous 12 months, and less than a third will eventually report it to the authorities. Many reasons have been used to explain why such a small proportion of sexual assaults are reported to authorities, including victim blaming attitudes. These attitudes are called Rape Myths and are defined as false beliefs about rape that are used to move the blame from the perpetrators to the victim.
Aims: The uIRMA, a 22-item scale, is the most established rape myth acceptance measure. While the psychometric properties of the uIRMA are excellent, no studies to date have assessed the latent structure of the scale through Item Response Theory (IRT). Furthermore, there is a lack of knowledge on the psychometric properties of the uIRMA with non-binary identifying persons.
Methodology: The sample is composed of N = 1636 participants from the general populations, composed of female (n = 896, 54.8%), male (n = 460, 28.1%) and non-binary identifying (n = 280; 17.1%).
Data analysis: Univariate analyses (i.e., frequency), Two-parameters Item Response Theory and Exploratory Factor Analysis will be presented.
Results: As hypothesized, the uIRMA is discriminating adequately across genders and items, with all items being within the recommended thresholds, further supporting the good psychometric properties of the scale. Furthermore, the difficulty level of corresponding items was lower for men than women and non-binary individuals, with men endorsing with more ease Rape Myth at all levels. However, analyses revealed psychometric concerns with the use of the uIRMA among non-binary participants, with few items being endorsed at b4 level, indicating that the scale might not be suitable for all genders.
Keywords: Rape Myths, Item Response Theory, Victim Blaming Attitudes, Sexual Violence, Gender Differences.