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DFIT (version 1.1)

Differential Functioning of Items and Tests

Description

A set of functions to perform Raju, van der Linden and Fleer's (1995, ) Differential Functioning of Items and Tests (DFIT) analyses. It includes functions to use the Monte Carlo Item Parameter Replication approach (Oshima, Raju, & Nanda, 2006, ) for obtaining the associated statistical significance tests cut-off points. They may also be used for a priori and post-hoc power calculations (Cervantes, 2017, ).

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Version

Install

install.packages('DFIT')

Monthly Downloads

445

Version

1.1

License

GPL (>= 2)

Maintainer

Victor H Cervantes

Last Published

August 17th, 2021

Functions in DFIT (1.1)

Calculates the asymptotic variance for difficulty parameter estimates under the 1pl model

Calculate1plProb

Calculates the item success probability under the 1PL model.

Calculate2plProb

Calculates the item success probability under the 2PL model.

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

Differential Functioning of Items and Tests framework

Cut-off points for Ipr generated estimates

ExtractRaschMirt

Extract item difficulties and item difficulty variance estimates for Rasch items from a fitted mirt object for one or two groups

Item parameter replication

Mantel Haenszel for Item parameter replication

CalculateGrmExp

Calculates the expected item score under the GRM model.

Calculates the asymptotic covariance matrix of item parameter estimates under the 3pl model

ExtractGPCMMirt

Extract item discrimination and difficulties and estimate covariance estimates for GPCM items from a fitted mirt object for one or two groups

Unsigned Area Measure for Item parameter replication

Signed Area Measure for Item parameter replication

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

NCDIF for Item parameter replication

Calculate3plProb

Calculates the item success probability under the 3PL model.

Extract item discrimination and difficulties and estimate covariance estimates for GRM items from a fitted mirt object for one or two groups

CalculatePcmExp

Calculates the expected item score under the (G)PCM model.

Calculate4plProb

Calculates the item success probability under the 4PL model.

Calculates CDIF index for an item with given item parameters of focal and reference groups.

Calculates Raju's Signed Area Measure index for an item with given item parameters of focal and reference groups.

Plot the item characteristic (expected score) curve for focal and reference groups for the iiItem along with a representation of the focal group density.

ExtractMirtPars

Extracts the item parameters from a unidimensional mirt model

Calculates Raju's Unsigned Area Measure index for an item with given item parameters of focal and reference groups.

ProductProbabilities

Calculates the product of item response probabilities for dichotomous IRT models

Calculates the asymptotic covariance matrices for item parameters according with the IRT model.

Calculates DTF index for a set of items with given item parameters of focal and reference groups.

Identifies items with guessing outside [0, 1]

CheckDiscriminations

Identifies items with nonpositive discrimination

Obtains the ETS Delta measure for Mantel-Haneszel DIF statistic effect size.

Extract item discrimination, difficulties, and guessing parameters and estimate covariance estimates for 3PL items from a fitted mirt object for one or two groups

CalculateItemDifferences

Calculates the differences between two item option characteristic curves for all options (minus one).

Extract item discrimination and difficulties and estimate covariance estimates for 2PL items from a fitted mirt object for one or two groups

Calculates the Mantel-Haenszel theoretical parameter when a dichotomous IRT model holds

dichotomousItemParameters

Sets of focal and reference item parameters from Wright (2011).

polytomousItemParameters

Sets of focal and reference item parameters from Raju et al. (2009)

Calculates NCDIF index for an item with given item parameters of focal and reference groups.

Calculates the asymptotic covariance matrix of item parameter estimates under the 2pl model

Takes item parameters from Ipr and forces guessing to lie between 0 and 1

Takes item parameters from Ipr and forces guessing to lie between 0 and 1