# Unequal sample sizes for two-way repeated measures

I have 3 different treatments with the observations of 6 different repetitions. However, all these different treatments (groups) have different numbers of patients. The first group has 26 patients, the second group has 28 patients and the third group has 19 patients. Thus, I can say that I have unequal sample sizes for two-way repeated measures anova.

When I do the analysis by using SPSS, it calculates the sum of squares and degrees of freedom by using the minimum sample size of the third group, which is 19.

Solving the problem and doing the comparisons by hand is time consuming. I would like to know how to handle this kind of problem, which is unequal sample sizes in each groups, by using the computer. Is there any other program, (SAS or R?) that deals with that, apart from SPSS, which obviously can not?

• – Ray Koopman Oct 12 '13 at 23:59

SAS proc mixed can to this. See their documentation. Unequal and unknown covariance matrices as well as unequal sample sizes are supported there. (I would recommend UN as covariance structure unless you are sure about a different structure, see the repeated statement.)