topic Re: Does gamma distribution carry out log-transformation in Statistical Procedures

Does gamma distribution carry out log-transformation

iaatoloye — Mon, 01 Jul 2024 15:11:21 GMT

When a gamma distribution is specified in SAS, does SAS perform a log transformation to achieve and satisfy the data normality assumption? I thought using a gamma distribution violates normal assumptions. @Rick_SAS

Thanks,

Re: Does gamma distribution carry out log-transformation

StatDave — Mon, 01 Jul 2024 15:11:47 GMT

The normality assumption does not apply to a generalized linear model using a distribution other than the normal distribution. See this note.

Re: Does gamma distribution carry out log-transformation

iaatoloye — Mon, 01 Jul 2024 15:18:39 GMT

Thanks. I am trying to edit this statement and thinking of knocking out the second part.

I would like to clarify if this is a valid statement or not: " A gamma distribution was used for all data analyses, for which a log-transformation was conducted by SAS to achieve data normality."

Re: Does gamma distribution carry out log-transformation

StatDave — Mon, 01 Jul 2024 15:23:09 GMT

If you fit a model using the gamma distribution for the response in the GENMOD, GLIMMIX, or other modeling procedure, then you can probably drop the phrase after the comma.