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Community Trekker


May 6, 2013

Which repeated measures method to use?

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

Re: Which repeated measures method to use?

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.