BACKGROUND For the Low Vision Quality Of Life questionnaire (LVQOL) it is unknown whether the psychometric properties are satisfactory when an item response theory (IRT) perspective is considered. This study evaluates some essential psychometric properties of the LVQOL questionnaire in an IRT model, and investigates differential item functioning (DIF). METHODS Cross-sectional data were used f...

In the analysis of differential item functioning (DIF) using item response theory (IRT), a common metric is necessary to compare item parameters between groups of test-takers. In the Rasch model, the same restriction is placed on the item parameters in each group in order to define a common metric. However, the question how the items in the restriction – termed anchor items – are selected appro...

Inter-group comparisons using the EQ-5D, or any self-reported measure of health, rely on the measure being an accurate reflection of the true health of the groups or individuals concerned. However, responses to questions on subjective scales, such as those used in the EQ-5D, will be inaccurate if groups of individuals systematically differ in their use of the response categories, a phenomenon k...

In this paper, two integrated Bayesian models for differential item functioning (DIF) analysis in item response theory (IRT) models are proposed and compared. The model is integrated in the sense of modelling the responses along with the DIF determination, thus allowing DIF detection and DIF explanation in a simultaneous setup. DIF occurs because item characteristics may change according to gro...

Abstract In latent scaling applications, such as the positioning of political parties, differential item functioning (DIF) may occur because measurement issues or substantive differences in association between and manifest variables. While first source DIF has received considerable attention, second not, although it is potential interest to comparative scholars. this research note, we introduce...

Submit Manuscript | http://medcraveonline.com encouraged give a lower score to an item about self-confidence than those from a country where more self-assured people are well-respected, even when their underground trait levels of selfconfidence are the same. In more psychometric terminology, this phenomenon—namely, unequal responding patterns among groups—is called differential item functioning...

OBJECTIVE Measures of shoulder function may differ by dominance of affected shoulder, surgical history, gender, or race. We present a technique for determining whether observed differences in function between groups are due to biased test items or real differences in function. STUDY DESIGN AND SETTING Four hundred patients who were receiving rehabilitation for a variety of shoulder impairment...

OBJECTIVES Estimates of group differences in functional disability may be biased if items exhibit differential item functioning (DIF). For a given item, DIF exists if persons in different groups do not have the same probability of responding, given their level of disability. This study examines the extent to which DIF affects estimates of age and gender group differences in disability severity ...

Recently, adaptive test approaches have become a viable alternative to traditional fixed-item tests. The main advantage of tests is that they reach desired measurement precision with fewer items. However, items mean each item has more significant effect on ability estimation and therefore those are open consequential results from any flaw in an item. So, indicating differential functioning (DIF...

BACKGROUND The SF-36 is a very commonly used generic measure of health outcome in osteoarthritis (OA). An important, but frequently overlooked, aspect of validating health outcome measures is to establish if items work in the same way across subgroup of a population. That is, if respondents have the same 'true' level of outcome, does the item give the same score in different subgroups or is it ...