sirt: dif.variance – R documentation

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sirt

dif.variance

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.