partgam_DIF: Partial Gamma to detect Differential Item Functioning (DIF)
Description
Items should function in the same way for all subgroups of persons. An item
shows differential item functioning (DIF) if there is a significant association between the item score and
an exogenous variable, controlling for the scale score. Partial Gamma coefficients are used as test statistics.
Usage
partgam_DIF(dat.items, dat.exo)
Arguments
dat.items
A data frame with the responses to the items.
dat.exo
A single grouping factor or a data frame consisting of several exogenous factor variables.
Value
data frame with Gamma coefficients, standard errors, p values and confidence limits for every
pair of an item and an exogenous variable.
References
Bjorner, J., Kreiner, S., Ware, J., Damsgaard, M. and Bech, P. Differential item
functioning in the Danish translation of the SF-36. Journal of Clinical Epidemiology,
51 (11), 1998, pp. 1189-1202.