Constrained Extended Plackett-Luce model for the analysis of preference rankings

Choice behavior and preferences typically involve numerous and subjective aspects that are difficult to be identified and quantified. For this reason, their exploration is frequently conducted through the collection of ordinal evidence in the form of ranking data. Multistage ranking models, including the popular Plackett-Luce distribution (PL), rely on the assumption that the ranking process is performed sequentially, by assigning the positions from the top to the bottom one (forward order). A recent contribution to the ranking literature relaxed this assumption with the addition of the discrete reference order parameter, yielding the novel Extended Plackett-Luce model (EPL). In this work, we introduce the EPL with order constraints on the reference order parameter and a novel diagnostic tool to assess the adequacy of the EPL parametric specification. The usefulness of the proposal is illustrated with an application to a real dataset.