I'm trying to compare three groups data. But the data set is about a new drug trial. The data set has these characteristics:
- Follow-up set. That is, after administration of the drug, a series of parameters were collected in the following date, day0, day1,day2,...,day28.
- Unbalanced set. Because some patients died and some recovered, not all patients were followed to 28 days; for instance, some were followed for only 20 days.
- Non normally distributed parameter. Especially, day25-day28, sometimes sd >> mean.
So, I try to use the linear mixed-effect model with
group*time for the comparison. ANOVA is not suit for the unbalanced set.
However, I wonder if it's correct model for non normal data set? Or is there another method suited for this kind of set?
I use SPSS 19. Some of my friends use STATA or JMP.