The Fourth WHOA-PSI will focus on emerging frontiers in post-selection inference, with particular emphasis on issues of accuracy, power and validity. More than 30 invited talks, and also Ph.D. student posters, will present recent advances in high-dimensional, selective, simultaneous, and Bayesian inference. Special attention is given to analytic and bootstrap-based refinements. New methodologies for model selection or change-point analysis may also be discussed, as well as relevant applications in need of post-selection inference procedures.