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RE: st: chi2 on aggregate results


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: chi2 on aggregate results
Date   Mon, 10 May 2010 18:31:04 +0100

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 
n.j.cox@durham.ac.uk 

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
<alan.neustadtl@gmail.com> 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 <mai7777@gmail.com> 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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