ltm: Latent Trait Models under IRT

Analysis of multivariate dichotomous and polytomous data using latent trait models under the Item Response Theory approach. It includes the Rasch, the Two-Parameter Logistic, the Birnbaum's Three-Parameter, the Graded Response, and the Generalized Partial Credit Models.

AuthorDimitris Rizopoulos <>
Date of publication2013-12-20 10:59:19
MaintainerDimitris Rizopoulos <>
LicenseGPL (>= 2)

View on CRAN

Man pages

Abortion: Attitude Towards Abortion

anova: Anova method for fitted IRT models

biserial.cor: Point-Biserial Correlation

coef: Extract Estimated Loadings

cronbach.alpha: Cronbach's alpha

descript: Descriptive Statistics

Environment: Attitude to the Environment

factor.scores: Factor Scores - Ability Estimates

fitted: Fitted Values for IRT model

gh: Gauss-Hermite Quadrature Points

GoF: Goodness of Fit for Rasch Models

gpcm: Generalized Partial Credit Model - Polytomous IRT

grm: Graded Response Model - Polytomous IRT

information: Area under the Test or Item Information Curves Item-Fit Statistics and P-values

LSAT: The Law School Admission Test (LSAT), Section VI

ltm: Latent Trait Model - Latent Variable Model for Binary Data

ltm-package: Latent Trait Models for Item Response Theory Analyses

margins: Fit of the model on the margins

Mobility: Women's Mobility

mult.choice: Multiple Choice Items to Binary Responses Person-Fit Statistics and P-values

plot: Plot method for fitted IRT models

plot.descript: Descriptive Statistics Plot method

plot.fscores: Factor Scores - Ability Estimates Plot method

rasch: Rasch Model

rcor.test: Pairwise Associations between Items using a Correlation...

residuals: Residuals for IRT models

rmvlogis: Generate Random Responses Patterns under Dichotomous and...

Science: Attitude to Science and Technology

summary: Summary method for fitted IRT models

testEquatingData: Prepares Data for Test Equating

tpm: Birnbaum's Three Parameter Model

unidimTest: Unidimensionality Check using Modified Parallel Analysis

vcov: vcov method for fitted IRT models

WIRS: Workplace Industrial Relation Survey Data


Abortion Man page
anova.gpcm Man page
anova.grm Man page
anova.ltm Man page
anova.rasch Man page
anova.tpm Man page
biserial.cor Man page
coef.gpcm Man page
coef.grm Man page
coef.ltm Man page
coef.rasch Man page
coef.tpm Man page
cronbach.alpha Man page
descript Man page
Environment Man page
factor.scores Man page
factor.scores.gpcm Man page
factor.scores.grm Man page
factor.scores.ltm Man page
factor.scores.rasch Man page
factor.scores.tpm Man page
fitted.gpcm Man page
fitted.grm Man page
fitted.ltm Man page
fitted.rasch Man page
fitted.tpm Man page
gh Man page
GoF.gpcm Man page
GoF.rasch Man page
gpcm Man page
grm Man page
information Man page Man page
LSAT Man page
ltm Man page
ltm-package Man page
margins Man page
margins.gpcm Man page
margins.grm Man page
margins.ltm Man page
margins.rasch Man page
margins.tpm Man page
Mobility Man page
mult.choice Man page Man page
plot.descript Man page
plot.fscores Man page
plot.gpcm Man page
plot.grm Man page
plot.ltm Man page
plot.rasch Man page
plot.tpm Man page
rasch Man page
rcor.test Man page
residuals.gpcm Man page
residuals.grm Man page
residuals.ltm Man page
residuals.rasch Man page
residuals.tpm Man page
rmvlogis Man page
rmvordlogis Man page
Science Man page
summary.gpcm Man page
summary.grm Man page
summary.ltm Man page
summary.rasch Man page
summary.tpm Man page
testEquatingData Man page
tpm Man page
unidimTest Man page
vcov.gpcm Man page
vcov.grm Man page
vcov.ltm Man page
vcov.rasch Man page
vcov.tpm Man page
WIRS Man page


ltm/R/vcov.rasch.R ltm/R/print.summ.ltm.R ltm/R/iprobs.R ltm/R/start.val.rasch.R ltm/R/scoregpcmSNW.R ltm/R/coef.ltm.R ltm/R/residuals.rasch.R ltm/R/jacobian.R ltm/R/residuals.gpcm.R ltm/R/vcov.gpcm.R ltm/R/ ltm/R/observedFreqs.R ltm/R/fscores.t.R ltm/R/print.unidimTest.R ltm/R/vcov.ltm.R ltm/R/logLiktpm.R ltm/R/rcor.test.R ltm/R/fscores.r.R ltm/R/probs.R ltm/R/fscores.g.R ltm/R/summary.grm.R ltm/R/descript.R ltm/R/loglikltm.R ltm/R/summary.gpcm.R ltm/R/summary.rasch.R ltm/R/print.information.R ltm/R/GoF.gpcm.R ltm/R/print.tpm.R ltm/R/summary.ltm.R ltm/R/ltm.R ltm/R/plot.ltm.R ltm/R/factor.scores.tpm.R ltm/R/cronbach.alpha.R ltm/R/tpm.R ltm/R/print.summ.grm.R ltm/R/testEquatingData.R ltm/R/infoGPCM.R ltm/R/grm.R ltm/R/simulate.grm.R ltm/R/print.margins.grm.R ltm/R/logLik.grm.R ltm/R/chisq.irt.R ltm/R/anova.ltm.R ltm/R/cumprobs.R ltm/R/vcov.grm.R ltm/R/IRT.parm.ltm.R ltm/R/print.aov.ltm.R ltm/R/coef.grm.R ltm/R/print.gpcm.R ltm/R/margins.grm.R ltm/R/GHpoints.R ltm/R/biserial.cor.R ltm/R/ ltm/R/print.aov.gpcm.R ltm/R/print.GoF.rasch.R ltm/R/infoprobs.R ltm/R/coef.tpm.R ltm/R/print.fscores.R ltm/R/factor.scores.grm.R ltm/R/matArrays.R ltm/R/print.rasch.R ltm/R/matches.R ltm/R/rmvlogis.R ltm/R/plot.gpcm.R ltm/R/rmvordlogis.R ltm/R/start.val.ltm.R ltm/R/EM.R ltm/R/anova.gpcm.R ltm/R/plot.fscores.R ltm/R/scoregpcm.R ltm/R/plot.grm.R ltm/R/crf.GPCM.R ltm/R/IRT.parm.tpm.R ltm/R/logLik.ltm.R ltm/R/betas.grm.R ltm/R/anova.tpm.R ltm/R/globals.R ltm/R/matMeans.R ltm/R/betas.ltm.R ltm/R/rasch.R ltm/R/GoF.rasch.R ltm/R/print.persFit.R ltm/R/scoretpm.R ltm/R/gpcm.R ltm/R/print.summ.rasch.R ltm/R/scoreltm.R ltm/R/anova.rasch.R ltm/R/coef.rasch.R ltm/R/fitted.grm.R ltm/R/print.grm.R ltm/R/residuals.grm.R ltm/R/start.val.gpcm.R ltm/R/summary.tpm.R ltm/R/plot.rasch.R ltm/R/fitted.rasch.R ltm/R/print.itemFit.R ltm/R/factor.scores.rasch.R ltm/R/print.summ.tpm.R ltm/R/plot.tpm.R ltm/R/crf.GPCM2.R ltm/R/print.aov.tpm.R ltm/R/fd.vec.R ltm/R/logLik.tpm.R ltm/R/plot.aov.gpcm.R ltm/R/simulate.gpcm.R ltm/R/betas.rasch2.R ltm/R/IRT.parm.grm.R ltm/R/loglikgrm.R ltm/R/gauher.R ltm/R/thetas.tpm.R ltm/R/ ltm/R/factor.scores.gpcm.R ltm/R/fitted.gpcm.R ltm/R/fitted.tpm.R ltm/R/margins.ltm.R ltm/R/plot.descript.R ltm/R/ ltm/R/print.rcor.test.R ltm/R/vcov.tpm.R ltm/R/margins.rasch.R ltm/R/print.aov.grm.R ltm/R/print.cronbachAlpha.R ltm/R/cd.tpm.R ltm/R/margins.tpm.R ltm/R/plot.unidimTest.R ltm/R/print.aov.rasch.R ltm/R/logLik.rasch.R ltm/R/margins.gpcm.R ltm/R/loglikgpcm.R ltm/R/anova.grm.R ltm/R/print.margins.gpcm.R ltm/R/cprobs.R ltm/R/print.GoF.gpcm.R ltm/R/fitted.ltm.R ltm/R/print.descript.R ltm/R/linpred.GPCM.R ltm/R/mult.choice.R ltm/R/IRT.parm.R ltm/R/matSums.R ltm/R/betas.gpcm.R ltm/R/cd.vec.R ltm/R/start.val.tpm.R ltm/R/start.val.grm.R ltm/R/print.summ.gpcm.R ltm/R/fscores.l.R ltm/R/margins.R ltm/R/scoregrm.R ltm/R/betas.rasch.R ltm/R/print.margins.ltm.R ltm/R/residuals.ltm.R ltm/R/print.ltm.R ltm/R/factor.scores.ltm.R ltm/R/logLik.gpcm.R ltm/R/factor.scores.R ltm/R/unidimTest.R ltm/R/residuals.tpm.R ltm/R/information.R ltm/R/coef.gpcm.R ltm/R/IRT.parm.rasch.R
ltm/man/rasch.Rd ltm/man/gpcm.Rd ltm/man/biserial.cor.Rd ltm/man/anova.Rd ltm/man/rmvlogis.Rd ltm/man/ ltm/man/WIRS.Rd ltm/man/information.Rd ltm/man/residuals.Rd ltm/man/unidimTest.Rd ltm/man/rcor.test.Rd ltm/man/Environment.Rd ltm/man/tpm.Rd ltm/man/grm.Rd ltm/man/ ltm/man/cronbach.alpha.Rd ltm/man/ltm-package.Rd ltm/man/LSAT.Rd ltm/man/mult.choice.Rd ltm/man/Science.Rd ltm/man/gh.Rd ltm/man/testEquatingData.Rd ltm/man/vcov.Rd ltm/man/plot.descript.Rd ltm/man/Abortion.Rd ltm/man/factor.scores.Rd ltm/man/fitted.Rd ltm/man/ltm.Rd ltm/man/Mobility.Rd ltm/man/descript.Rd ltm/man/margins.Rd ltm/man/plot.Rd ltm/man/GoF.Rd ltm/man/plot.fscores.Rd ltm/man/coef.Rd ltm/man/summary.Rd

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