[R-sig-ME] Mixed model with counts data

[Chun (Jimmie) Ye]

Hi all,

I have a rather peculiar dataset that I'm not sure how to model
properly. This is data from an instrument that measures the size of
particles but instead of giving a continuous value, it generates a
"histogram" of the counts for a particular bin size. So the data looks
like this:

	Condition 1				Condition 2			
Dimension	Rep1.A	Rep1.B	Rep2.A	Rep2.B	Rep1.A	Rep1.B	Rep2.A	Rep2.B
2	5	6	7	8	40	35	33	31
2.1	7	8	4	5	30	30	31	29
2.2	10	11	10	12	20	18	21	20
2.3	50	45	44	39	5	8	7	7
2.4	80	90	75	77	8	10	3	5
3.5	30	22	31	35	10	5	7	9
…								
50	0	0	0	0	0	0	1	0

There are two biological replicates and two technical replicates for
each of the conditions of interest. If these were continuous, I would
just fit a nested mixed model to the data. But instead, I have counts.
I was thinking that this might be suitable for modeling using a
multinomial response. I could also just compare the distribution using
a KS test but I'm not sure how to incorporate the replicate
information (except for averaging). Finally, I thought perhaps I could
estimate directly from the histogram the variance components from the
data. Any thoughts is greatly appreciated!

~Jimmie