by Dimitris Rizopoulos

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Date 2013-12-20
LazyLoad yes
LazyData yes
License GPL (>= 2)
Packaged 2013-12-20 09:11:59 UTC; drizopoulos
NeedsCompilation no
Repository CRAN
Date/Publication 2013-12-20 10:59:19

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.

Functions in ltm

Name Description
coef Extract Estimated Loadings
cronbach.alpha Cronbach's alpha
anova Anova method for fitted IRT models
Environment Attitude to the Environment
descript Descriptive Statistics
biserial.cor Point-Biserial Correlation
fitted Fitted Values for IRT model
gh Gauss-Hermite Quadrature Points Item-Fit Statistics and P-values
WIRS Workplace Industrial Relation Survey Data
gpcm Generalized Partial Credit Model - Polytomous IRT
factor.scores Factor Scores - Ability Estimates
ltm Latent Trait Model - Latent Variable Model for Binary Data
rcor.test Pairwise Associations between Items using a Correlation Coefficient
grm Graded Response Model - Polytomous IRT
rmvlogis Generate Random Responses Patterns under Dichotomous and Polytomous IRT models
information Area under the Test or Item Information Curves
testEquatingData Prepares Data for Test Equating Person-Fit Statistics and P-values
plot IRT Plot method for fitted IRT models
residuals Residuals for IRT models
mult.choice Multiple Choice Items to Binary Responses
plot descript Descriptive Statistics Plot method
unidimTest Unidimensionality Check using Modified Parallel Analysis
margins Fit of the model on the margins
plot fscores Factor Scores - Ability Estimates Plot method
vcov vcov method for fitted IRT models
rasch Rasch Model
Mobility Women's Mobility
Science Attitude to Science and Technology
Abortion Attitude Towards Abortion
LSAT The Law School Admission Test (LSAT), Section VI
tpm Birnbaum's Three Parameter Model
GoF Goodness of Fit for Rasch Models
summary Summary method for fitted IRT models
ltm-package Latent Trait Models for Item Response Theory Analyses
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