Running repeated measures in lme4

Hi Everyone,

Thanks for your replies in response:

Yes my data are

site	treatment		minutes
1	1			15
1	2			16
1	3			60
1	4			35
2	1			
2	2
2	3
2	1

etc

Regards the repeated measures element: although I only have one replicate 
of each treatment level, the subject is site and at each site I repeatedly 
measured the response across treatments, treatments 1-4 were sequentially 
measured on each subject.

Regards using the model1<-lmer~(minutes~treatment+(1|site), data = data)

"The intercept value for the response is allowed to vary randomly between 
sites - the unit that has been measured repeatedly. ". Forgive me for 
sounding stupid, but I am not sure that I really understand this, if this 
is the site level variation in the intercept of the response, isnt this my 
group level effect regardless of treatment? If so how can it be accounting 
for the repeated measures, as the repeated measures are treatments within 
sites.

I am not interested in the between sites differences in intercepts - 
overall site level effects in themselves, i.e. I don't care if there is a 
difference between sites in terms of intercept, as I would expect there to 
be as they are a random selection of sites, which all start with different 
actual values.

I am interested in how the response changes between treatments within site 
- and whether this pattern (slope) is the same across sites. So I 
understand that I am after the within subject effects of treatment across 
sites, therefore - whether the effect of treatment is the same across sites 
(the slope), if it significantly different between sites, there is no 
overall effect of treatment.

I then would want to conduct post hocs to test which treatment levels are 
significantly different from each other.

I have run this model (from the same design) with a different data set in 
SPSS and it runs fine, there are enough degrees of freedom as I have 4 
treatments and 8 sites.

I tried using a poisson model because I used the unlogged data.

Thanks

Emma

--On 03 March 2010 14:24 +0100 "Andy Fugard (Work)" <andy.fugard at sbg.ac.at> 
wrote:

Running repeated measures in lme4

Thread (2 messages)