Multiple comparison tests are variants on the two-sample t-test.
They use the pooled standard deviation sp = √MSE.
The pooled degrees of freedom DFE.
And they compensate for the multiple comparisons.
We compute the t-statistic for all pairs of means:
A given test is significant (µi and µj significantly different), when
|tij| ≥ t** (df = DFE).
The value of t** depends on which procedure you choose to use.