We put forward a model based on item response theory that highlights the role of latent features called “proficiency” and “propensity”. The model is adjusted to data from the decisions made in a high-stakes exam taken by 10,822 Brazilian high school students. Our model aims to recover information regarding the role the latent features (proficiency and propensity) play in a decision. We find that the decision of responding or not and also the decision of responding correctly or not in a group of items can be described by a two-dimensional logistic model, even if there are imperfections from an item-by-item adjustment. Not only proficiency, but also refraining from responding is found to depend on both the characteristics of the items and the latent features of the students. In particular, the least proficient students prefer to leave an item blank, rather than respond it incorrectly. There is a negative linear correlation between scoring in the exam and propensity, and scoring and proficiency are positively correlated although nonlinear.