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RE: st: chi2 on aggregate results
From
"Nick Cox" <[email protected]>
To
<[email protected]>
Subject
RE: st: chi2 on aggregate results
Date
Mon, 10 May 2010 19:17:37 +0100
It's the same test; it's just a question of which way you look at it, in terms of null hypothesis or not, and of how pedantically (carefully) you word it.
Nick
[email protected]
mai7777
Interesting. So if the tabi test is for the independence of the row &
column vars, how can I test that the proportions are statistically
different given the sample sizes?
On Mon, May 10, 2010 at 1:31 PM, Nick Cox <[email protected]> wrote:
> No; it is not. 47.22 and 76.67 are observed column percents, and not predictions of the hypothesis.
>
> The hypothesis being tested is that the row and column variables are independent. This may be clearer if you also use the -expected- option of -tabi-.
>
> Nick
> [email protected]
>
> mai7777
>
> Thanks for the quick response. I guess it was the "col" option that I
> was looking for, but just to confirm: Below, is the Pearson chi2(1) =
> 5.9421 Pr = testing the hypothesis that the proportion of 76.67 in
> a sample size of 30 equal to the proportion of 47.22 in a sample size
> of 36?
>
>
> . tabi 23 17 \ 7 19, chi col
> | col
> row | 1 2 | Total
> -----------+----------------------+----------
> 1 | 23 17 | 40
> | 76.67 47.22 | 60.61
> -----------+----------------------+----------
> 2 | 7 19 | 26
> | 23.33 52.78 | 39.39
> -----------+----------------------+----------
> Total | 30 36 | 66
> | 100.00 100.00 | 100.00
>
> Pearson chi2(1) = 5.9421 Pr = 0.015
>
>
> On Mon, May 10, 2010 at 1:15 PM, Alan Neustadtl
> <[email protected]> wrote:
>> Are you looking for something like this?
>>
>> - tabi 23 17 \ 7 19, chi col -
>>
>>
>>
>> On Mon, May 10, 2010 at 1:08 PM, mai7777 <[email protected]> wrote:
>>> hi,
>>> I'm trying to conduct a chi2 on aggregate results to test that the
>>> proportions of incidence across two treatments are the same:
>>>
>>> Treatment 1 has a total of 30 subjects, 23 of which had incidence
>>> Treatment 2 has a total of 36 subjects, 17 of which had incidence.
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