Re: st: Question on Ttest.

[Richard Williams <Richard.A.Williams.5@nd.edu>]

At 12:47 PM 11/21/2003 +0000, Joao Pedro W. de Azevedo wrote:
> Dear Statausers,
> I'm doing a simple ttest, however I would like to retrive the Std. Deviation
> of the difference of the means (see output below). Does anyone know if Stata
> saves this statistic?
> Many thanks,
> JP
>
>
> . ttest  match2291_0== match2291_1 if week>=2144
I'm not a heavy-duty Stata user and somebody may be able to give you 
exactly the answer you want.  But, given that this is matched pairs, I 
think you might be able to improvise as follows:

. gen diff2291 = match2291_0 - match2291_1
. ttest diff2291 == 0 if week>=2144

In other words, compute the difference between the two scores and then do a 
1-sample t-test of whether the mean of that difference is zero.  From that 
retrieve the standard error of the difference.


-------------------------------------------
Richard Williams, Associate Professor
OFFICE: (574)631-6668, (574)631-6463
FAX:    (574)288-4373
HOME:   (574)289-5227
EMAIL:  Richard.A.Williams.5@ND.Edu
WWW (personal):    http://www.nd.edu/~rwilliam
WWW (department):    http://www.nd.edu/~soc

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/