A Flexible IRT Model for Health Questionnaire: An Application to HRQoL
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The aim of this study is to formulate a suitable Item Response Theory (IRT) based model to measure HRQoL (as latent variable) using a mixed responses questionnaire and relaxing the hypothesis of normal distributed latent variable. The new model is a combination of two models, that is a latent trait model for mixed responses and an IRT model for Skew Normal latent variable. It is developed in a Bayesian framework. The proposed model was tested on a questionnaire composed by 5 discrete items and one continuous to measure HRQoL in children. The new model has better performances, in term of Deviance Information Criterion, Monte Carlo Markov chain convergence times and precision of the estimates.