# How to check if data is normally distributed

Hi all,

I want to run a f-test on two samples to see if their variances are independent. Wikipedia says that the f test is sensitive to non normality of sample (<http://en.wikipedia.org/wiki/F-test)>. How can I check if my samples are normally distributed or not.

I read some forums which said I can use kstest and lillietest. When can I use either? I get an answer h=0. Does that mean my data is normally distributed?

*NOTE:-*

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You cannot tell from only 2 samples whether they are normally distributed or not. If you have a larger sample set and you are only testing them in pairs, then you could use the larger sample set to test for a particular distribution.

For example: (simple q-q plot)

data= randn(100); %generate random normally distributed 100x100 matrix

ref1= randn(100); %generate random normally distributed 100x100 matrix

ref2= rand(100); %generate random uniformly distributed 100x100 matrixx=sort(data(:));

y1=sort(ref1(:));

y2=sort(ref2(:));subplot(1,2,1); plot(x,y1);

subplot(1,2,2); plot(x,y2);

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