Body Appreciation Scale (BAS-2): Measurement Invariance across Genders and Item Response Theory Examination.

Abstract

Background: The present study considers a measure of positive body image, the Body Appreciation Scale-2, which assesses acceptance and/or favourable opinions towards the body (BAS-2[29]). Differential functioning of the scale across the two genders, as well as its items, has not been excluded. The present study contributes to this area of knowledge via the employment of gender Measurement Invariance (MI) and Item Response Theory (IRT) analyses. Methods: A group of 386 adults from the community were assessed (N = 394, 54.8% men, 43.1% women, M age = 27.48; SD = 5.57). Results: MI analysis observed invariance across males and females at the configural level, and non-invariance at the metric level. Further, the two-parameter logistic model employed to observe IRT properties indicated that all items demonstrated, although variable, strong discrimination capacity. Conclusions: The items showed increased reliability for latent levels of ∓ 2 SD from the mean level of Body Appreciation. The implications and interpretations of the findings for clinical practice are discussed.

Warwick Edinburgh Mental Well-Being Scale (WEMWBS): measurement invariance across genders and item response theory examination

“…For clarification purposes, those endorsing easier items are said to have lower SWB. Conversely, those who endorse the difficult items are said to have higher SWB ([ 26 , 85 ]).

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“…Note : ICC expresses in a nonlinear (logit) regression line pertaining to difficulty (β) and discrimination (α) parameters. Difficulty (β) indicates the level of the latent trait where there is a .5 probability that a participant will endorse a specific criterion or item [ 85 ]. For example, ‘easier’ items have lower β values and their ICC is represented closer to the horizontal axis.…”

“…Whilst IRT models were initially established to evaluate dichotomous data (i.e., yes/no), extensions of these models have been employed to accommodate the use of ordered polytomous data (i.e., more than two response options reflecting order/ranking [ 26 , 85 ]). Given that the WEMWBS measures SWB with a 5-point scale (with multiple and incrementally ordered answers per item), the use of IRT models suitable for polytomous data is required [ 85 ]. In that framework, “Rasch” models assume equal discrimination (α) across items and behave as 1PL models [ 20 ].…”

“…In that framework, “Rasch” models assume equal discrimination (α) across items and behave as 1PL models [ 20 ]. Contrarily, the generalised partial credit (GPC) and graded response models (GRM) assume variable item discrimination properties (α), and present more suitable for ordered polytomous data [ 26 , 85 ].…”

“…Specifically, Multigroup Confirmatory Factor Analysis (MCFA) can be employed in the evaluation of MI because it enables structural comparisons at various levels including: configural (i.e., factorial structure); metric (i.e., factor loadings); scalar (i.e., intercepts and thresholds); and strict (i.e., residuals) invariance [ 31 , 54 ]. In this regard, acquiring configural invariance suggests that the pattern of item-factor loadings along with the number of factors within the WEMWBS are alike for men and women [ 85 ]. Moreover, attaining metric invariance for the WEMWBS would suggest that the item-factor loading relationship is being measured with the same metric scale for both groups [ 69 ].…”