Hi Natalie,

It sounds like a mixed model might be appropriate but it's not completely
clear what your data are like. How many levels are there of each factor? Or
is each factor just binary (treatment or no treatment)? What did you measure
as the response? It's a good idea to post a sample of your data, or at least
some dummy data with the same structure, so that we can see what it's like.

It sounds like you don't have pseudo replication but you do have repeated
measures (same animal used for more that 1 observation) and missing
observations (not all treatment / treatment combinations measured for each
animal). A mixed effects model with a random effect for animal might be
appropriate but it would depend on how many animals you have, how many
treatment combos there were and how many treatment combos each animal got on
average. Also knowing the order treatments were given to each animal might
help.



Andy.





andydolman@gmail.com


2009/4/29 nat_h <fbsnch@leeds.ac.uk>

>
> Hi,
>
> I have an experiment with 2 independant factors which I have been trying to
> analyse in R. The problem is that there are several data points recorded on
> the same animal. However, no combination of treatments  is repeated on the
> same animal. All possible combinations of treatments are done in a random
> order with as many points as possible being done on 1 animal before moving
> onto the next.
>
> The suggested way to remove pseudoreplication is to average the points from
> the same animal. However, as my measures on the same animal are of
> different
> treatment combinations so this makes no sense. It is also suggested that as
> I have random and fixed effects I should use a mixed effects model.
> However,
> given that my independant variables are factorial I am not sure how to
> incorporate this. I would be very grateful for any advice on methods of
> getting round this problem or whether I have sufficiently accounted from my
> none independant measures experimentally.
>
> Many thanks,
>
> Natalie
> --
> View this message in context:
> http://www.nabble.com/2-way-ANOVA-with-possible-pseudoreplication-tp23295845p23295845.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]


