Dear Ecologgers, I would like to ask for advice concerning the design and statistical analysis of an experiment. My problem is described below.
I have made crosses by applying the same mixture of pollen from two pollen donors (provenance 1 and 2) on one mother plant of each of the two same provenances (a mother couple), with a total of 16 mother plants (8 per provenance). I now want to investigate the performance of the resulting offspring (hybrids, pure provenance 1, pure provenance 2). A difficulty is that the genotypes are unknown at the time of the start of the experiment, and will only be known after a genetic analysis of the leaf material. I will use two experimental conditions: wet and dry. For practical reasons, it is easier to vary the water factor for the whole germination trays. Ive got 6 experimental tables that can hold each a maximum of 3 germination trays with 104 seeds each. Considering the tables as replicates, I will assign 2 trays to each table and have the wet and dry treatments randomly assigned to trays within each table. Thus, the ingredients I have got are: max. 6 tables [replicates or blocks] 2 water treatments 2 provenances 8 families or mothers (nested in provenance) 2 genotypes [pure and hybrid] Two possible options are: a) I grow 6 seeds of each of the 16 mother plants (completely randomized within tray) in each of 8 trays on 4 tables. Given that I dont know the genotypes, this will lead to unequal sample sizes for genotype and, in the worst case, to missing genotypes in certain trays. b) I assign all seeds of two mother couples (4 x 24) to one randomly selected tray and thus, confound mothers and block. Given that Im interested in estimating differences in performance related to genotype and provenance (hybrids, pure provenance 1, pure provenance 2), but not in variability between families, 1) which design is the more suitable/optimal (confounding/ power) for the question I am most concerned about? Or is there still a better one? 2) Do I have a split-split plot design with an additional nested factor? What about the statistical evaluation of the results? Please feel free to email me off list ([EMAIL PROTECTED]). Sincerely, Madlen *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~**~*~*~*~*~*~*~*~* Madlen Denoth, PhD Département de Biologie/Ecologie & Evolution Université de Fribourg/Pérolles Chemin du Musée 10 1700 Fribourg Suisse Tel. ++41 26 300 88 48 email: [EMAIL PROTECTED] "Too often we enjoy the comfort of opinion without the discomfort of thought. " -- John F. Kennedy *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~**~*~*~*~*~*~*~*~*
