What is differential item functioning analysis?
Differential item functioning (DIF) methods are a range of techniques that are increasingly being used to evaluate whether different subgroups respond differently to particular items within a scale, after controlling for group differences in the overall HRQoL domain being assessed.
What is the main concept of Rasch model?
The Rasch model is built on the assumption that the most parsimonious and effective predictor of a trait is the relationship between the difficulty of an item and the ability of a person.
What is uniform differential item functioning?
Abstract. Uniform differential item functioning (DIF) exists when the statistical relationship between item response and group is constant for all levels of a matching variable.
What is dif in psychometrics?
Differential item functioning (DIF) is the preferred psychometric term for what is otherwise known as item bias. An item displays DIF when test takers possessing the same amount of an ability or trait, but belonging to different subgroups, do not share the same likelihood of correctly answering the item.
What is IRT ICC?
Item Response Function and Item Characteristic Curve (ICC) IRT models predict respondents’ answers to an instrument’s items based on their position on the latent trait continuum and the items’ characteristics, also known as parameters. Item response function characterizes this association.
What is the purpose of Rasch analysis?
Specifically, Rasch analysis allows researchers to use a respondent’s raw test or scale scores and express the respondent’s performance on a linear scale that accounts for the unequal difficulties across all test items.
What is dif in Rasch?
Differential Item Functioning (DIF) investigates the items in a test, one at a time, for signs of interactions with sample characteristics. In the widely used Mantel-Haenszel procedure (1959, www.rasch.org/memo39.pdf, RMT 1989 3:2 51-53), reference and focal groups are identified which differ in a discernible way.
What is Item separation reliability?
Item separation is used to verify the item hierarchy. Low item separation (< 3 = high, medium, low item difficulties, item reliability < 0.9) implies that the person sample is not large enough to confirm the item difficulty hierarchy (= construct validity) of the instrument.
What is IRT scaling?
IRT models can identify dataset items with different difficulty levels and discrimination powers based on human responses, and identify items that are not appropriate as scale items for evaluation. The resulting small set of items can be used as a scale to score an individual or NLP system.
How is Rasch model calculated?
di=Y(xi-x.) The fit of data to the Rasch model can be evaluated by calculating how much is “left over” after the data have been used to estimate item difficulties di and person abilities bn = br, where r is the test score of person n.
Does the Rasch model fit the latent trait?
Moreover, all four items that were resolved showed evidence of DIF, with girls scoring more problems than boys given the same location on the latent trait. Following resolution of items, all items fitted the Rasch model; however, there is no guarantee that they should do so.
Can the Rasch model be used for dichotomous data?
The Rasch model can be used for analysis of dichotomous [ 6] as well as polytomous data [ 7 ]. In principle there are only two kinds of parameters to be estimated in the Rasch model, item and person parameters which enter into the model additively.
How is differential item functioning (DIF) assessed in the hospital scale?
A comparison of three methods of assessing differential item functioning (DIF) in the Hospital Anxiety Depression Scale: ordinal logistic regression, Rasch analysis and the Mantel chi-square procedure. Qual Life Res. 2014;23:2883–8. 5. Cho S-J, Suh Y, Lee W.
Which Rasch model is used in the DIF-analysis?
The DIF-analysis was conducted using the polytomous Rasch model [ 16 ]. Because the data are used for illustrative purposes, only gender DIF is analysed while also DIF across time as well as other violations of the Rasch model may occur.