Researcher J. E. Kennedy has said that concerns over the use of meta-analysis in science and medicine apply as well to problems present in parapsychological meta-analysis. As a post-hoc analysis, critics emphasize the opportunity the method presents to produce biased outcomes via the selection of cases chosen for study, methods employed, and other key criteria. Critics say that analogous problems with meta-analysis have been documented in medicine, where it has been shown different investigators performing meta-analyses of the same set of studies have reached contradictory conclusions.