ltm: An R package for latent variable modeling and item response theory analyses

JSS Journal of Statistical Software November 01/2006; 17.

ABSTRACT The R package ltm has been developed for the analysis of multivariate dichotomous and polytomous data using latent variable models, under the Item Response Theory ap-proach. For dichotomous data the Rasch, the Two-Parameter Logistic, and Birnbaum's Three-Parameter models have been implemented, whereas for polytomous data Seme-jima's Graded Response model is available. Parameter estimates are obtained under marginal maximum likelihood using the Gauss-Hermite quadrature rule. The capabilities and features of the package are illustrated using two real data examples.

1 Bookmark
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract This paper explores four Item Response Theory (IRT) models to determine the most appropriate for understanding item non-response. The selected IRT model was used to identify among five categories of survey questions, the most difficult to answer by respondents and determine the underlying mechanism behind missing data which is defined to include ‘don’t know’ answers. A questionnaire data on Ghana collected in the fifth wave of the World Values Survey was implored. All items were dichotomously scored. Missing or ‘don’t know’ responses were assigned a 0 score whiles answered items were assigned a 1 score. The four IRT models that were explored included both the constrained and unconstrained versions of the Rasch model, the two parameter logistic model (2-PLM), and the three parameter logistic model (3-PLM). The unconstrained Rasch model emerged as the most appropriate model for understanding item non-response. It was observed that, income related questions had the highest difficulty parameter, hence the most difficult category of survey questions to answer. It was also found that, if an individual does not answer a survey question or give a ‘don’t know’ answer, it is not only due to the question’s difficulty but also because the respondent doesn’t want to answer.
    Journal of Mathematical Theory and Modeling. 01/2014; Vol.4(No.3):pp. 33-40.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The modern economic theories consider human capital as a key factor for the long-term growth of a nation. In an educational contest a way to invest in human capital is to promote events that stimulate students to use communication technologies and to learn scientific reasoning. Therefore the Italian Statistical Society (SIS) support the National Olympics of Statistics, involving the second grade middle schools. The questionnaire of the competition has been analyzed in this paper through IRT models to evaluate its quality in discriminating students ability.
    Procedia - Social and Behavioral Sciences 10/2013; 93:2194–2199.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this study was to demonstrate the use of the Rasch model by assessing the appropriateness of the demographic, social-economic and geographic factors in providing a total score in malaria RDT in accordance with the model's expectations. The baseline malaria indicator survey was conducted in Amhara, Oromiya and Southern Nation Nationalities and People (SNNP) regions of Ethiopia by The Carter Center in 2007. The result shows high reliability and little disordering of thresholds with no evidence of differential item functioning.
    International journal of environmental research and public health. 01/2014; 11(7):6681-6691.


Available from