Demystify Lindley's Paradox by Interpreting P-value as Posterior Probability

Abstract: In the hypothesis testing framework, p-value is often computed to determine rejection of the null hypothesis or not. On the other hand, Bayesian approaches typically compute the posterior probability of the null hypothesis to evaluate its plausibility. We revisit Lindley's paradox (Lindley, 1957) and demystify the conflicting results between Bayesian and frequentist hypothesis testing procedures by casting a two-sided hypothesis as a combination of two one-sided hypotheses along the opposite directions. This can naturally circumvent the ambiguities of assigning a point mass to the null and choices of using local or non-local prior distributions. As p-value solely depends on the observed data without incorporating any prior information, we consider non-informative prior distributions for fair comparisons with p-value. The equivalence of p-value and the Bayesian posterior probability of the null hypothesis can be established to reconcile Lindley's paradox. Extensive simulation studies are conducted with multivariate normal data and random effects models to examine the relationship between the p-value and posterior probability.