The present study has two main interests. First, some pending issues about the psychometric properties of the CTAC (an anxiety questionnaire for blind and visually-impaired people) are assessed using item response theory (IRT). Second, the linear model is compared to the graded response model (GRM) in terms of measurement precision, sensitivity to change, and person fit, and the results are also used to illustrate the functioning and advantages of IRT models. The participants were 670 blind or visually-impaired people from different Spanish cities. The results showed that the CTAC scores are accurate enough for practical purposes, and that respondents are quite consistent in their responses. Model-data fit was acceptable in both cases, and both models lead to similar results regarding the trait estimates, with the exception of extreme respondents who were better assessed with the linear model. The GRM assessed measurement precision better, and both models showed high sensitivity to change around cut-off values. Person-fit results were also similar in both models.

Open Access