Apply tests of multiple comparisons based
on studentized 'midrange' and 'range' distributions.
The tests are: Tukey Midrange ('TM' test),
Student-Newman-Keuls Midrange ('SNKM' test),
Means Grouping Midrange ('MGM' test) and
Means Grouping Range ('MGR' test). The first two tests were published by
Batista and Ferreira (2020)