breslowDay {difR}R Documentation

Breslow-Day DIF statistic

Description

Computes Breslow-Day statistics for DIF detection.

Usage

breslowDay(data, member, anchor=1:ncol(data))
 

Arguments

data numeric: the data matrix (one row per subject, one column per item).
member numeric: the vector of group membership with zero and one entries only. See Details.
anchor a vector of integer values specifying which items (all by default) are currently considered as anchor (DIF free) items. See Details.

Details

breslowDay computes the Breslow-Day statistic (1980) in the specific framework of differential item functioning. It forms the basic command of difBD and is specifically designed for this call.

The data are supplied by the data argument, with one row per subject and one column per item. Missing values are not allowed.

The vector of group membership, specified by the member argument, must hold only zeros and ones, a value of zero corresponding to the reference group and a value of one to the focal group.

Option anchor sets the items which are considered as anchor items for computing Breslow-Day DIF statistics. Items other than the anchor items and the tested item are discarded. anchor must hold integer values specifying the column numbers of the corresponding anchor items. It is primarily designed to perform item purification.

Value

A matrix with one row per item and three columns: the first one contains the Breslow-Day statistic values, the second column indicates the degrees of freedom, and the last column displays the asymptotic p-values.

Author(s)

Sebastien Beland
Centre sur les Applications des Modeles de Reponses aux Items (CAMRI)
Universite du Quebec a Montreal
sebastien.beland.1@hotmail.com
David Magis
Research Group of Quantitative Psychology and Individual Differences
Katholieke Universiteit Leuven
David.Magis@psy.kuleuven.be, http://ppw.kuleuven.be/okp/home/
Gilles Raiche
Centre sur les Applications des Modeles de Reponses aux Items (CAMRI)
Universite du Quebec a Montreal
raiche.gilles@uqam.ca, http://www.er.uqam.ca/nobel/r17165/

References

Breslow, N.E. and Day, N.E. (1980). Statistical methods in cancer research, vol. I: The analysis of case-control studies. Scientific Publication N° 32. International Agency for Research on Cancer, Lyon, France.

See Also

difBD, dichoDif

Examples

# Loading of the verbal data
data(verbal)

# With all items as anchor items
breslowDay(verbal[,1:24], verbal[,26])

# Removing item 3 from the set of anchor items
breslowDay(verbal[,1:24], verbal[,26], anchor=c(1:5,7:24))

[Package difR version 1.1 Index]