Should GraphPad Prism report adjusted P values?
Computing the adjusted P value is trivial for Bonferroni multiple comparison tests. It is harder for Tukey and Dunnett tests, as it requires computing critical values beyond those that have been tabulated. But this is possible. We are considering including adjusted P values as part of the reporting of one-way ANOVA with Tukey, Bonferroni or Dunnett multiple comparison tests. I hesitate to do this because I am not convinced the results would be useful, and fear that they will be misinterpreted. The only programs i know that computes adjusted P values is SAS. They do not seem to be mainstream. Please let us know if you would like to see adjusted P values in future versions of Prism, and explain why. Also please let me if you know of any other programs, papers or books that deal with multiplicity adjusted P values.
