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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
>> *
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>
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