dif.variance {sirt}

DIF Variance

Description

This function calculates the variance of DIF effects, the so called DIF variance (Longford, Holland & Thayer, 1993).

Usage

dif.variance(dif, se.dif, items=paste("item", 1:length(dif), sep="") )

Arguments

dif

Vector of uniform DIF effects

se.dif

Standard error of uniform DIF effects

items

Optional vector of item names

Value

A list with following entries

weighted.DIFSD

Weighted DIF standard deviation

unweigted.DIFSD

DIF standard deviation

mean.se.dif

Mean of standard errors of DIF effects

eb.dif

Empirical Bayes estimates of DIF effects

References

Longford, N. T., Holland, P. W., & Thayer, D. T. (1993). Stability of the MH D-DIF statistics across populations. In P. W. Holland & H. Wainer (Eds.). Differential Item Functioning (pp. 171-196). Hillsdale, NJ: Erlbaum.

See Also

See dif.logistic.regression for examples.