Item Analysis of a Selected Bank from the Voluntary HIV-1 Counseling and Testing Efficacy Study Group

A 15-item questionnaire, that is part of the HIV-1 VCT dataset, has been considered in this paper, following a Rasch analysis – by means of the Partial Credit Model. We begin by reviewing the different methods of maximum likelihood estimation of the parameters of the model. We then focus on five among the most popular Rasch measurement softwares that implement these estimation methods. The questionnaire results to have the qualities of a good measure of attitude, in the population, towards the use of the condom- but a gender-based Differential Item Functioning has been detected for several items in the test.