topic Re: Help interpreting estimates using log link function in GENMOD in Statistical Procedures

Help interpreting estimates using log link function in GENMOD

FSHN — Thu, 21 Jul 2016 16:48:43 GMT

Dear Help Community,

I'm trying to understand how to interpret my estimates in the table below. I'm using GENMOD with a NEGBIN model and log link function. Are my estimates transformed, and are they log10 or natural log transformed? How can I get my response variable back to my original unit? FYI, the response is colony forming units of bacteria.

proc genmod data=liver;

class Sex Diet;

model CFU=Sex|Diet/ Link=log Dist=NEGBIN type1 type3;

LSmeans Sex|Diet/Lines;

run;

Diet Least Squares Means
Diet	Estimate	Standard Error	z Value	Pr > \|z\|
A	6.8394	0.01524	448.84	<.0001
B	9.7593	0.002296	4249.98	<.0001
C	8.5384	0.02500	341.52	<.0001
D	8.4607	0.003765	2247.04	<.0001
E	14.9283	0.000149	100409	<.0001

Re: Help interpreting estimates using log link function in GENMOD

SteveDenham — Thu, 21 Jul 2016 18:09:21 GMT

The estimates are on the natural log scale. To get values on the original scale, use the ILINK option in the LSMEANS statement.

Steve Denham

Re: Help interpreting estimates using log link function in GENMOD

FSHN — Fri, 22 Jul 2016 13:55:33 GMT

Steve,

Perfecto! Thanks for the natural log confimation and ILINK trick.