Model selection using union-intersection principle for non nested models

In this article, we have extended the Vuong’s (1989) model selection test to three models in accordance to union-intersection principle. Using the Kullback–Leibler criterion to measure the closeness of a model to the truth, we propose a simple likelihood ratio-based statistics for testing the null hypothesis that the competing models are equally close to the true data-generating process against the alternative hypothesis that at least one model is closer. We show that the distribution of the test statistic is asymptotically equal to the distribution of the maximum of dependent random variables with bivariate folded standard normal distribution. The density function of the maximum of dependent random variables with elliptically contoured distributions has been obtained by other researchers, but, not for distributions which do not belong to the elliptically contoured distributions family. In this article, the exact distribution of the maximum of dependent random variables with bivariate folded standard normal distribution is calculated as an asymptotic distribution of the proposed test statistic. The test is directional and is derived successively for the cases where the competing models are non nested and whether three, two, one, or none of them are misspecified.