Summary statistics & plots of repeated measures data
Jay Pfaffman <pfaffman at relaxpc.com> writes:
I'd like to see the effects of each of the treatments for this
within-subject comparison. Repeated measures ANOVA seems like the
analysis I need. The results of
summary(lme(ete ~ treatment, data=allitems, random=~1 | studentkey,
subset=allitems$classkey==4))
follow, but I'm not quite sure what to make of them. In particular,
I'm very confused about the meanings of the numbers in the Value
column, as they bear no relation to the group means of the data in
each of those treatments.
They're not supposed to. Not in an unbalanced design. Mostly, if there is a substantial variation between students, the results would be closer to that obtained from an additive linear model treating student effects as fixed (lm(ete ~ treatment+factor(studentkey), ...)). The treatment means is what you get if you assume zero student variation, and in general you get some sort of average between the two. You'll bump into those issues whatever program you choose...
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907