Hi Meaghan, Linear regression models assume that the residuals of the response variable are normally distributed. Predictor variables iinstead are not assumed to have a normal distribution. Not even to be random variables. In fact, there assumed to take valueswhich are fixed a-priori. Although this assumtion is often false, it can be relaxed if the error in the determination of the predictor values is small relative to the range of values included in the model. These things are nicely explained in Draper & Smith 1981 Applied Regression Analysis. Wiley w
At 03:28 p.m. 13/11/2007, you wrote: >can you normalize this variable through one of the various methods of >normalization? > >On Tue, November 13, 2007 10:46 am, Sami Ullah wrote: > > Hey Ecologers: > > > > I have a various variables for running multiple linear regression model > > using GLM. Some of my predictor variables are non-normally distributed. > > Using multiple linear regression, I use proc-univariate to check if the > > residuals in the regression model met the normality criteria, which the > > model did. > > > > Now I am wondering if it is advisable if I can keep the skewed predictor > > variables in the model or have to go for non-parametric analysis? > > > > Thanks > > Meaghan Murphy, > > Ph.D. Candidate > > > > >Malcolm L. McCallum >Assistant Professor of Biology >Editor Herpetological Conservation and Biology >http://www.herpconbio.org >[EMAIL PROTECTED] >[EMAIL PROTECTED] > > >-- >No virus found in this incoming message. >Checked by AVG Free Edition. >Version: 7.5.503 / Virus Database: >269.15.31/1130 - Release Date: 14/11/2007 09:27 a.m. > > > > >-- >No virus found in this incoming message. >Checked by AVG Free Edition. >Version: 7.5.503 / Virus Database: >269.15.31/1130 - Release Date: 14/11/2007 09:27 a.m. William B. Batista Facultad de Agronomía UBA Av. San Martín 4453 1417DSE Buenos Aires Argentina Tel: +54-11-4524-8077 www.agro.uba.ar/users/batista -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.15.31/1130 - Release Date: 14/11/2007 09:27 a.m.
