[R-sig-ME] lmer or glmer?

Michael Jackson Michael.Jackson at vuw.ac.nz
Mon Jan 12 20:41:03 CET 2015

Hi Thierry,

Thanks for the input. Ive attached some links to qqnorm(resid(x)) plots run for varying data.

Plot 1 (link below) (based on lmer code) is characteristic of all my plots when using my raw data, i.e., showing positive skew to a greater or lesser extent than this example. I identified the response variable as key to driving this and therefore tried log transforming my response variable.

Plot 2 is the same raw data and lmer coding, but with a log transformed response variable. It now shows slight negative skew and if anything is worse.

Plot 3 is from my glmer coding I proposed in my first message (the two former used the lmer coding) and also my raw untransformed response or predictors. This looks lots better. A SW test is also not significant (p=0.67). This is actually based on using "family=poisson(link=log)" as ive now read that the "family=" aspect only relates to the response, not predictors ...Id be interested in your thoughts.

Plot 1 http://s166.photobucket.com/user/michaeljackson1972/media/Plot1_zps1e8eb440.png.html

Plot 2 http://s166.photobucket.com/user/michaeljackson1972/media/Plot2_zpsa5e555b8.png.html

Plot 3 http://s166.photobucket.com/user/michaeljackson1972/media/Plot3_zpsf4a5b638.png.html

Thanks again,


PhD Candidate
Centre for Biodiversity and Restoration Ecology
Room KK 411
Kirk Building
Kelburn Parade
Wellington 6012

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