Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.

# Re: st: obtain SD from P value for a paired t-test

 From Marcos Vinicius <[email protected]> To [email protected] Subject Re: st: obtain SD from P value for a paired t-test Date Wed, 2 Oct 2013 04:20:10 -0800

```Thank you Steve.
Regards,
Marcos
> -----Original Message-----
> From: [email protected]
> Sent: Tue, 1 Oct 2013 18:37:59 -0400
> To: [email protected]
> Subject: Re: st: obtain SD from P value for a paired t-test
>
>
> Marcos:
>
>
> You can't get the SD post without knowing the correlation of the pre &
> post measurements,
> since:
>
> sd_diff = sqrt ( sd_pre^2 + sd_post^2  - 2 rho sd_pre sd_post)
>
> Steve
> On Oct 1, 2013, at 1:56 PM, Marcos Vinicius wrote:
>
> better formulating the question :obtaining the SD of the post measure
> using the   information bellow and additionally we know the N for the
> paired t test.
>
> Vinicius
> -----Original Message-----
> From: [email protected]
> Sent: Tue, 1 Oct 2013 09:48:14 -0800
> To: [email protected]
> Subject: Re: st: obtain SD from P value for a paired t-test
>
> Thanks Rich but not solved yet.
> I know the N,so I can get the standard deviation of the
> diference(post-pre).
> However I still don t know if it is possible to obtain the standard
> deviation corresponding to the post measure.
> Vinicius
>> -----Original Message-----
>> From: [email protected]
>> Sent: Tue, 01 Oct 2013 13:04:47 -0400
>> To: [email protected]
>> Subject: Re: st: obtain SD from P value for a paired t-test
>>
>> if you know N also, you can use the formula given in the Stata manual
>> (methods and formulas section of the ttest entry in the reference
>> manual), or many texts, to get the sd - if you don't know N, the best
>> you can do is an approximation
>>
>> Rich
>>
>> On 10/1/13 12:09 PM, Marcos Vinicius wrote:
>>> Hello,
>>> Anyone knows a way to obtain  standard deviation(sd) from P value for a
>>> paired t-test.?
>>> Consider that I know:
>>> Average pre
>>> SD pre
>>> Average post
>>> SD post (to be determined from others parameters)
>>> P value from paired t test
>>>
>>> Average pre=6.5
>>> SD pre=1.8
>>> Average post =4.9
>>> SD post ??(to be determined from others parameters)
>>> P value from paired t test p=0.0003
>>> Any help would be greatly appreciated
>>> Thanks
>>> Vinicius
>> *
>> *   For searches and help try:
>> *   http://www.stata.com/help.cgi?search
>> *   http://www.stata.com/support/faqs/resources/statalist-faq/
>> *   http://www.ats.ucla.edu/stat/stata/
>
> ____________________________________________________________
> FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on
> Check it out at http://www.inbox.com/marineaquarium
>
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/
>
> ____________________________________________________________
> FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on
> Check it out at http://www.inbox.com/marineaquarium
>
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/

____________________________________________________________
FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on your desktop!
Check it out at http://www.inbox.com/marineaquarium

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/
```