Familywise and per-family error rates of multiple comparison procedures.

In multiple testing scenarios, one of the more popular definitions of the error rate is the familywise error rate (FWER). The per-family error rate (PFER) is often not considered. The PFER deserves more attention than it currently receives. Both of these concepts were formulated by Tukey. We highlight some of the good and bad qualities of the FWER and the PFER. We find the FWER and PFER for four commonly used multiple comparison procedures.