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Which repeated measures method to use?


Community Trekker


May 6, 2013

I am trying to figure out the best method of repeated measures analysis. Here is what I have. 19 years of data collected at 259 grid cells each. Data collected at each grid cell each year (for a total of 4921 observations) includes relative species abundance for 6 species, total acreage shellfish aquaculture and further those aquaculture totals split by acres cultivated of clams, geoduck, oysters and mussels. I am trying to see if there is a relationship between acres shellfish cultivated and bird relative abundances over 19 years, including how might each species respond differently, and how to responses differ by shellfish cultivated.

I have performed a mixed model repeated measures analysis for each species (for a total of 6 analyses) using the following construct model effects: acres (nominal bin, 11 bins total); gridcell[acres] & Random; year; acres*year

I have unsure if I am running the best analysis of my data and would appreciate any advice or feedback.

Thank you!


Community Trekker


Jun 23, 2011

How is relative species abundance distributed?  I'm guessing it is highly skewed and non-normally distributed.  You may need to run this model using Proc GLIMMIX in SAS and specify a negative binomial or poisson distribution for the errors.  I don't think you can do this in JMP.