Mode Estimation for Discrete Distributions

The problem of estimating the mode of a discrete distribution is considered. New characterizations of discrete unimodal and multi-modal distributions are obtained. The proposed mode estimator is essentially the sample mode, modulo appropriate modifications when the sample mode is not well defined. In the case of i.i.d. observations coming from a unimodal discrete distribution, our proposed mode estimator is shown to possess a number of strong asymptotic properties. Many of these results extend to the case of multi-modal discrete distributions as well. Our method also applies - and we have similar asymptotic results - to the problem of mode estimation based on finitely many observations on a Markov chain whose equilibrium distribution is the underlying unimodal distribution. For unimodal discrete distributions, we also propose a consistent large sample test of mode based on the proposed statistic. Applications of mode estimation problem in Monte-Carlo optimization problem using the Hastings Metropolis chain and in prediction problem using binary response variable, specially in the context of dose-response experiments, are also illustrated.