The "post-mortem" testing of experimental comparisons.

In an experimental design the investigator frequently wishes to go beyond an over-all analysis of variance F test, and seeks to examine specific means or totals from certain groups of treatments. In the a posteriori ("post-mortem") situation, where comparisons are suggested by examining the data, and have not been pre-planned, it is inappropriate to use the tabular F and t values, since these values are not based upon randomly selected observation. A procedure is recommended to handle this situation, one that avoids the danger of erroneous inferences (spuriously significant comparisons). (PsycINFO Database Record (c) 2010 APA, all rights reserved)