[R-sig-ME] individual Linear mixed models

[Etn]

Hi all,

I would be very grateful if you could please give any advice...
I am running a linear mixed model on a complete randomised block experiment

blocks = 11
treatments = 5 (A,B,C,D,E)
data recorded on days 1, 2, 11 and 18

I'm interested in looking at the difference between treatments on a
particular day
e.g. difference between treatments on day 1
(I am not interested in the difference between treatments on day 1 versus
day 11 etc.)

My question is: Is it OK to run linear mixed regression models on each day
individually? as I'm not concerned with the changes over time.....
(Results for individual days show a difference between treatments on day 1
and day 2, and no difference between treatments on day 11 and 18 - this
follows with what would be expected in reality)

fit <- lme(y ~ Treatment,  random = ~1|block)

Following this I run a tukey HSD to find comparison between treatments


Is this the correct approach ? any advice is greatly appreciated

Aside: I did try a more complicated model:
fit <- lme(y ~ Treatment*day,  random = ~1|block/day)
however none of the treatments were significant and it only showed that day
11 and day 8 were significantly different)



Many thanks

Etn

	[[alternative HTML version deleted]]