Item Response Theory Applied to the Spiritual Needs Questionnaire (SpNQ) in Portuguese

Abstract

The item response theory (IRT), or latent trace theory, is based on a set of mathematical models to complement the qualitative analysis of the items in a given questionnaire. This study analyzes the items of the Spiritual Needs Questionnaire (SpNQ) in the Portuguese version, applied to HIV+ patients, with R Studio 3.4.1, mirt statistical package, to find out if the items of the SpNQ possess appropriate psychometric qualities to discriminate between respondents as to the probability of marking one answer and not another, in the same item, showing whether or not the questionnaire is biased towards a pattern of response desired by the researcher. The parameters of discrimination, difficulty, information, and the characteristic curve of the items are evaluated. The reliable items to measure the constructs of each of the five dimensions of the SpNQ of this HIV+ sample (Religious Needs; Inner Peace and Family Support Needs; Existential Needs; Social Recognition Needs; and Time Domain Needs) are presented, as well as the most likely response categories, depending on the latent trace level of the individuals. The questionnaire items showed satisfactory discrimination and variability of difficulty, confirming the good psychometric quality of SpNQ.