Thanks Ilmari and Mark,
I'm happy to update the section in the 7.0 Calc Guide (which is
currently in preparation) but I'm still confused. Why does the z-test
tool think that the variance of the given data sets is zero? As you say
Ilmari, that is not a number that the user currently enters.
Regards,
Steve
------ Original Message ------
From: "Ilmari Lauhakangas" <[email protected]>
To: [email protected]
Sent: 02/09/2020 11:40:06
Subject: Re: [libreoffice-documentation] Calc's Z-test tool
Thanks! That was my gut feeling.
So the immediate action would be to change the screenshots in Help and Calc
guide so the variance cells have non-zero values, also adding a note to the
instructions.
A further question is, should we consider adding fields for inputting variance
values into the Z-test tool itself? Looking at Microsoft Office docs, Excel has
these. This would become an enhancement request in Bugzilla.
Ilmari
Mark Morin kirjoitti 2.9.2020 klo 2.57:
Variance can't be zero for analysis of variance tests (t test, F test,
etc). Statistical testing assumes that you have variance otherwise you
really wouldn't need a test.
On 9/1/2020 4:48 PM, Ilmari Lauhakangas wrote:
I was looking at a bug report again:
https://bugs.documentfoundation.org/show_bug.cgi?id=132983
The reporter is scratching their head over the "division by zero"
result for z.
From what I can see, the "Known variance" values can't both be zero,
if you want to avoid the #DIV/0! results. You have to give at least
one of them a positive non-zero value.
Now, looking at Help:
https://help.libreoffice.org/7.1/en-US/text/scalc/01/statistics_test_z.html
and the Calc guide chapter CG7009-DataAnalysis-SF-12Aug2020, we see
this same "division by zero" result and the reader is left holding it.
How to present this better in the docs? I have no experience on the
topic, but I hope we can find some statistician to shed light on this!
Ilmari
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