The first phase of simplification in sample A
REGRESSION
There were two stages included in this study. The first phase was used for simplification of the CRHLS in Sample A. The two-parameter logistic model (2PLM), one of the IRT models, was used to predict the probability of a successful answer for each item in each dimension (Where The information about individuals was based on their responses to items and the properties of all the items (Furthermore, in order to present how each dimension of scale was functioning as a whole, we also combine the item-level information functions to create a test information function, shown as test information curves (TIC). The standard errors were the square root of the inverse of information at a given level of ability. The item, with a discrimination parameter of 0.5 to 2.0 and a difficulty parameter of −3.0 to 3.0, was considered to provide the most information (Moreover, Differential Item Functioning (DIF) was used to test the equivalence of items. We applied logistic regression for identification of DIF using the ability (θ) derived from IRT analysis as the matching variable. This method has been used in previous published studies (In brief, if any of the following criteria was met in this phase, the item would be removed from original CRHLS: (a) discrimination(α) <0.5 or > 2.0 (