Fail normality test but the qqplot is a straight line

Asked Oct 30 '16 at 09:13

Active Oct 30 '16 at 12:00

Viewed 62 times

I am using SAS 9.4 . My aim is to find out whether my residual is normal or not, so i type this:

proc univariate data= residual normal; var rstd; qqplot rstd/ norml(mu=est sigma=est); run;

In my output the qqplot is clearly a straight while 4 pavlue of statistic for the normality is less then 5%.

How can i interpret this?

edited Oct 30 '16 at 12:00

asked Oct 30 '16 at 09:13

Gillian Cheung

1

Can you show the qq-plot? – JAD Oct 30 '16 at 09:21
currently i don't have the computer but i can tell you the points are nearly falling on the normal line , no heavytailness – Gillian Cheung Oct 30 '16 at 09:25
without the plot we are not going to be able to help you. – mdewey Oct 30 '16 at 11:22
3

What is your sample size? If it is large, then the p value will be low even for tiny violations of normality – Peter Flom Oct 30 '16 at 11:48
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my sample size is 270,and i have attached the photos – Gillian Cheung Oct 30 '16 at 11:52
What do you mean by "4 pavlue"? Can you edit? – kjetil b halvorsen Oct 30 '16 at 12:00
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"In my output the qqplot is clearly a straight". That is a subjective statement. IMO it is not clearly a straight line. – Jorge Leitao Oct 30 '16 at 12:03
so in my case,it is possibly due to the large number of n? – Gillian Cheung Oct 30 '16 at 12:46
See also: [Is normality testing 'essentially useless'?](http://stats.stackexchange.com/q/2492/7290) – gung - Reinstate Monica Oct 30 '16 at 13:00

0 Answers0