topic Re: How to test if a sample has a Normal Distribution? in Statistical Procedures

How to test if a sample has a Normal Distribution?

Wagner_Alvarenga — Fri, 26 Jul 2013 15:07:21 GMT

Hi,

I have a small Sample (with 30 points/observations) as variable "Sample" inside a Data Set named 'Data'.

I would like to know how to test if the this sample has a Normal Distribution.

Thanks!

Doc_Duke — Fri, 26 Jul 2013 15:35:12 GMT

PROC UNIVARIATE has multiple tests for normality. None of the tests are very powerful, so I'll also look at the plots for an eyeball test.

SteveDenham — Mon, 29 Jul 2013 18:38:34 GMT

And if the sample size is large (N>100) the tests are over-powered, where even small deviations can lead to a significant result.

Follow Doc's advice and look at the plots, especially the pp and qq plots.

Steve Denham

Rick_SAS — Tue, 30 Jul 2013 17:41:13 GMT

This should get you started:

ods graphics on;

PROC UNIVARIATE DATA=sashelp.iris(where=(Species="Virginica"));

VAR SepalLength;

histogram SepalLength / Normal;

qqplot SepalLength / Normal;

RUN;