Factorial invariance, differential item functioning, and norms of the Orgasm Rating Scale

Background/Objective: Orgasm Rating Scale (ORS) assess the subjective orgasm experience in context of sexual relationship. It is composed of four dimensions attributed to the orgasm (Affective, Sensory, Intimacy, and Rewards). The purpose is to analyse the factorial invariance of the ORS across groups, to examine the metric equivalence across sex, and to present the standard scores. Method: A total of 1,472 Spanish adults (715 men and 757 women) were evaluated. They were distributed across age groups (18-34, 35-49 and 50 years old and older). Factorial invariance across different groups and the differential functioning of the items across sex were analyzed, internal consistency was examined, and the standard scores were developed. Results: The structure of the ORS showed strict measurement invariance across sex, relationship status, sexual orientation and education level. It also reached a scalar measurement invariance across age range and duration of the relationship. Some items showed a differential functioning between sexes. Conclusions: The Spanish version of the ORS is invariant across different groups at a factorial level, and it shows equivalence across sex in most of its items at a metric level. The standard scores allow a more accurate assessment of the subjective orgasm experience in context of sexual relationship. (C) 2018 Asociacion Espanola de Psicologia Conductual. Published by Elsevier Espana, S.L.U.