----------------------------------------
> From: brave...@gmail.com
> Date: Fri, 23 Apr 2010 12:23:50 +0200
> To: itext-questions@lists.sourceforge.net
> Subject: Re: [iText-questions] performance follow up
>
> Hello Mike,
>
> On Apr 23, 2010, at 12:55 AM, Mike Marchywka wrote:
>
>> Mark Twain gets to the front so quickly. Again, I'm not suggesting
>> you did anything wrong or bad, I haven't actually checked numbers
>> or given the specific test a lot of thought- 9 data points is usually
>> not all that conclusive in any case and I guess that's my point.
>>
> There are 10 means, each mean comes from 1K data points, so there are 10K
> data points for each version tested, not just 9
I thought you had 9 test cases but 9 or 10 doesn't matter much.
>
> Unlike other tests of significance, t-test doesn't need a large number of
> observations. It is actually this case of "few observations" e.g. 10
yeah, personally I've never liked nonparametrics and other approaches
that magically work with a few samples. Generally they treat the
small sample cases by dealing with outliers ( outliars LOL? ) more
gracefully. However, if you make some assumptions about population
statistics and run monte carlo you can see how often your 9 or 10 points
with your chosen test lead to misleading results. This is a bit of
an inverse problem- you have data with contributions from many sources
( ie noise ) and you are trying to estimate some underlying clean
number- known approaches to this have limits.
>means one of its main use-cases. Indeed one would need to check the
>assumptions of independence and normality. Looking at the response times
Cache warmness could lead to lots of run-to-run dependence depending
on what you measure and I
know personally I see this with second invokation of various command
line programs. If as you suggest the distro is normal maybe it is
just a bunch of random junk but sometimes you see multi-modal
and each peak is probably due to something interesting.
In any case, the point here is to make the code faster and use
the stats or whatever other meaures you have to point the way.
>
> Best regards,
> Giovanni
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