I am having difficulty in properly specifying the error structure for an
experiment that is being analysed using the lme() function.  Physically,
I have 15 plots. Each plot contains 8 subplots.  Each subplot is
measured at 3 different times.  One treatment variable (L), containing 3
levels, is randomly assigned to the whole plots; thus there are 5
replicate plots for each of the 3 levels of L.  Two other treatment
variables (K, F), each having 2 levels, are randomly assigned to the
subplots within each plot; thus there are 2 replicates of each
combination of K and F in each of the 15 plots.

The fixed formula is y~L*K*F*time.  What is the proper formula for the
random effects?  I had thought that it was random=~1|L/plots/subplots
(i.e. subplots nested within plots nested within the L treatments) but
this is wrong because, using this formula, I have no degrees of freedom
for the L term.

 

Bill Shipley

Associate Editor, Ecology

North American Editor, Annals of Botany

Département de biologie, Université de Sherbrooke,

Sherbrooke (Québec) J1K 2R1 CANADA

Bill.Shipley@USherbrooke.ca

 <http://callisto.si.usherb.ca:8080/bshipley/>
http://callisto.si.usherb.ca:8080/bshipley/

 


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