Programming the statistical procedures from SAS

Normality for Proc mixed

Reply
N/A
Posts: 1

Normality for Proc mixed

I have a non-normal data. Do I need to make it normal (by appropriate transformation) prior to "Proc mixed" with "random" statement?

Respected Advisor
Posts: 2,655

Re: Normality for Proc mixed

If you know the distribution from which the data is generated, then PROC GLIMMIX will suit your needs.  Unusual links (transformations) can be handled programmatically.

If you are determined to use PROC MIXED, then the key is making the RESIDUALS normal.  For instance, a bimodal distribution due to sex can never be made "normal" and the analysis does not require that the response variable be normal--only that the residuals be normally and identically distributed.

Steve Denham

Super User
Posts: 9,753

Re: Normality for Proc mixed

Fisher's Z transform could help you to normalize it .

z=1/2* log( (1+x)/(1-x) )

Super Contributor
Posts: 426

Re: Normality for Proc mixed

Any possibilities to provide me an example of Fisher's Z transform?

Super Contributor
Posts: 426

Re: Normality for Proc mixed

Seems Fisher's Z transform is part of correlation. Will it work for single variable?

Super User
Posts: 9,753

Re: Normality for Proc mixed

Yeah. I think it should be worked on a single variable. It is just a transform function . But I don't how good it is, You can test it.

Of course. Don't forget try to use LOG() to make the variable normal too.

Respected Advisor
Posts: 2,655

Re: Normality for Proc mixed

Fisher's Z really only transforms values that are bounded below by -1 and above by 1 into normal deviates.

Steve Denham

Ask a Question
Discussion stats
  • 6 replies
  • 387 views
  • 0 likes
  • 4 in conversation