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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: Question about TestUtils.chiSquare
Date Mon, 01 Sep 2008 02:44:46 GMT


I doubt that you really want a chi^2 test for this in any case.  You could
use it if you binned the amounts so that you are comparing counts, but you
would only find out if there was a difference, not whether there was an
interesting difference.

Most likely, what you want is an unpaired, one-sided t-test because the real
question is whether one option or the other will produce higher mean revenue
per visitor.

You might also have some use for a Kolmogorov-Smirnov test for difference in
distribution.  It would be much more appropriate for (nearly) continuous
values such as purchase amounts.


Yannick-19 wrote:
> 
> Hello,
> 
> I'm wondering why the chi-square test has this API:
> 
> chiSquareTest(double[] expected, long[] observed) 
> 
> -
> I would think the type of expected and observed should be the same (for
> example, both double, like in the situation I have, where my series
> consists of purchase amounts on a website under two different
> conditions). 
> 
> Am I missing something trivial? Why is there no chiSquareTest(double[]
> expected, double[] observed) test?
> 
> Thanks!
> 
> Yannick
> 
> 
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