Differential Functioning of Items and Tests

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Documentation for package ‘DFIT’ version 1.1

• DESCRIPTION file.
• Code demos. Use demo() to run them.
• Package NEWS.

Help Pages

Ase1pl	Calculates the asymptotic variance for difficulty parameter estimates under the 1pl model
Ase2pl	Calculates the asymptotic covariance matrix of item parameter estimates under the 2pl model
Ase3pl	Calculates the asymptotic covariance matrix of item parameter estimates under the 3pl model
AseIrt	Calculates the asymptotic covariance matrices for item parameters according with the IRT model.
Bound3PlIpr	Takes item parameters from Ipr and forces guessing to lie between 0 and 1
Bound4PlIpr	Takes item parameters from Ipr and forces guessing to lie between 0 and 1
Calculate1plProb	Calculates the item success probability under the 1PL model.
Calculate2plProb	Calculates the item success probability under the 2PL model.
Calculate3plProb	Calculates the item success probability under the 3PL model.
Calculate4plProb	Calculates the item success probability under the 4PL model.
CalculateGrmExp	Calculates the expected item score under the GRM model.
CalculateItemDifferences	Calculates the differences between two item option characteristic curves for all options (minus one).
CalculatePcmExp	Calculates the expected item score under the (G)PCM model.
Cdif	Calculates CDIF index for an item with given item parameters of focal and reference groups.
CheckDiscriminations	Identifies items with nonpositive discrimination
CheckGuessings	Identifies items with guessing outside [0, 1]
CheckUpper	Identifies items with upper asymptote outside [0, 1]
CrossedProbabilities	Calculates the crossed probabilities associated with the numerator and denominator of the odds-ratio under dichotomous IRT models
CutoffIpr	Cut-off points for Ipr generated estimates
DeltaMhIrt	Obtains the ETS Delta measure for Mantel-Haneszel DIF statistic effect size.
DFIT	Differential Functioning of Items and Tests framework
dichotomousItemParameters	Sets of focal and reference item parameters from Wright (2011).
Dtf	Calculates DTF index for a set of items with given item parameters of focal and reference groups.
Extract2PLMirt	Extract item discrimination and difficulties and estimate covariance estimates for 2PL items from a fitted mirt object for one or two groups
Extract3PLMirt	Extract item discrimination, difficulties, and guessing parameters and estimate covariance estimates for 3PL items from a fitted mirt object for one or two groups
Extract4PLMirt	Extract item discrimination, difficulties, guessing, and upper asymptote parameters and estimate covariance estimates for 4PL items from a fitted mirt object for one or two groups
ExtractGPCMMirt	Extract item discrimination and difficulties and estimate covariance estimates for GPCM items from a fitted mirt object for one or two groups
ExtractGRMMirt	Extract item discrimination and difficulties and estimate covariance estimates for GRM items from a fitted mirt object for one or two groups
ExtractMirtPars	Extracts the item parameters from a unidimensional mirt model
ExtractRaschMirt	Extract item difficulties and item difficulty variance estimates for Rasch items from a fitted mirt object for one or two groups
Ipr	Item parameter replication
IprMh	Mantel Haenszel for Item parameter replication
IprNcdif	NCDIF for Item parameter replication
IprSam	Signed Area Measure for Item parameter replication
IprUam	Unsigned Area Measure for Item parameter replication
IrtMh	Calculates the Mantel-Haenszel theoretical parameter when a dichotomous IRT model holds
Ncdif	Calculates NCDIF index for an item with given item parameters of focal and reference groups.
PlotNcdif	Plot the item characteristic (expected score) curve for focal and reference groups for the iiItem along with a representation of the focal group density.
polytomousItemParameters	Sets of focal and reference item parameters from Raju et al. (2009)
ProductProbabilities	Calculates the product of item response probabilities for dichotomous IRT models
SignedArea	Calculates Raju's Signed Area Measure index for an item with given item parameters of focal and reference groups.
UnsignedArea	Calculates Raju's Unsigned Area Measure index for an item with given item parameters of focal and reference groups.