Inference for a two-component mixture of symmetric distributions under log-concavity

In this article, we revisit the problem of estimating the unknown zero-symmetric distribution in a twocomponent location mixture model, considered in previous works, now under the assumption that the zerosymmetric distribution has a log-concave density. When consistent estimators for the shift locations and mixing probability are used, we show that the nonparametric log-concave Maximum Likelihood estimator (MLE) of both the mixed density and that of the unknown zero-symmetric component are consistent in the Hellinger distance. In case the estimators for the shift locations and mixing probability are √n-consistent, we establish that these MLE's converge to the truth at the rate n^-2/5 in the L₁ distance. To estimate the shift locations and mixing probability, we use the estimators proposed by (Ann. Statist. 35 (2007) 224-251). The unknown zero-symmetric density is efficiently computed using the R package logcondens.mode.