partgam_DIF function

Partial Gamma to detect Differential Item Functioning (DIF)

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.

partgam_DIF(
  dat.items,
  dat.exo,
  p.adj = c("BH", "holm", "hochberg", "hommel", "bonferroni", "BY", "none")
)

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.
• p.adj: Correction method for multiple testing. The methods are "BH","holm", "hochberg", "hommel", "bonferroni", "BY", "none". See p.adjust.

Returns

data frame with Gamma coefficients, standard errors, p values, adjusted p values if an adjustment method has be chosen, and confidence limits for every pair of an item and an exogenous variable.

Examples

partgam_DIF(amts[,4:13],amts[,2:3])

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.

See Also

partgam_LD

Author(s)

Marianne Mueller