This program calculates areas in the tails of the Studentized Range Distribution. First specify the value of the studentized range
statistic (Q). Q is computed as follows:

Some programs compute the value of the studentized t by including a 2 in the
denominator. If so, then you should multiply the t by 2.77 to convert it to
Q.

Then specify the number of means in the experiment and the degrees of freedom
(df). Click the "OK" button and the two-tailed probability will be shown
at the bottom.