What does differential item functioning DIF indicate about an item?

What does differential item functioning DIF indicate about an item?

Differential item functioning (DIF) is a statistical characteristic of an item that shows the extent to which the item might be measuring different abilities for members of separate subgroups.

What is differential item functioning used for?

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 differential item functioning in psychology?

Overview. In brief, differential item functioning (DIF) occurs when groups (such as defined by gender, ethnicity, age, or education) have different probabilities of endorsing a given item on a multi-item scale after controlling for overall scale scores.

What is differential test functioning?

Differential test functioning, or DTF, occurs when one or more items in a test demonstrate differential item functioning (DIF) and the aggregate of these effects are witnessed at the test level. In many applications, DTF can be more important than DIF when the overall effects of DIF at the test level can be quantified.

What is reliability index?

Item reliability index is equal to the product of the discrimination and standard deviation of the item. So item realibility index=rjx.Sx. This index can be calculated for dichotomous or polytomous item type. Allen & Yen (1979) explained this index in their book.

What is differential validity?

The concept of differential validity suggests that cognitive ability tests are associated with varying levels of validity across ethnic groups, such that validity is lower in certain ethnic subgroups than in others.

What is nonuniform DIF?

DIF occurs when there is no interaction between ability level and group membership. Nonuniform DIP occurs. when there is interaction between ability level and group membership. In general, although uniform DIP. occurs more often than nonuniform DIP in standardized tests, n®nunif® ly functioning items have been.

What is the difference between single group and differential validity?

Single-group validity means that a test is valid for one group (usually whites) but is invalid (that is, has zero validity) for other groups (typically members of minority groups). Differential validity refers to a situation where a test is predictive for all groups but to different degrees.

What are the different types of validity?

The different types of validity that are important to survey research include construct validity, convergent validity, content validity, representation validity, face validity, criterion validity, concurrent validity, predictive validity, statistical conclusion validity, internal validity, external validity, and …