Hello all, I hope I have found the right place for my question. There are different kinds of p-values for one-sided and two-sided tests, for example mid p-value [1], minimum-likelihood p-value [2] or conditional two-sided p-value [3]. I tried to find out what kind of p-value is implemented in R with regard to the two-sided chi-square (function chisq.test()) and Spearman rank test (function cor.test() with method="spearman"), but I could not determine this from the documentation or the source. I would be thankful if someone with a better understanding could provide an explanation. [1] J. D. Gibbons, J. W. Pratt. P-Values: Interpretation and Methodology. 1975 [2] I. Rivals, L. Personnaz, L. Taing, M. C. Potier. Enrichment or depletion of a GO category within a class of genes: which test?. 2006 [3] E. Kulinskaya. One two-sided p-values for non-symmetrical distributions. 2007 Best regards, Vincent