Can someone clue me in as to how degrees of freedom are calculated for Dunnett's test for multiple comparisons? We have a data set with 5 groups (1 control and 4 treated). The n-numbers are 16, 16, 16, 15, and 16, respectively. The stat package we're using (TOXSTAT) gives output that shows the degrees of freedom as 24,4. The 4, I get (K-1, where K=5). But I can't for the life of me figure out the 24. I thought that DF would be the summation of n-1, but obviously that's not even close. What am I missing? Thanks.