R: Differential Functioning of Items and Tests

# Differential Functioning of Items and Tests

## 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.