Hi Michael,
What you said sounds definitely quite reasonable, thank you. But we were asked to 'formally test if the negative result was due to our statistical power' for a publication. So we dont have much choice.
On Sun, 22 Jan 2012 11:17:39 -0600, Michael Harms <[log in to unmask]> wrote:
>Hi Sinan,
>Post-hoc power-analyses of that sort are not really meaningful.
>By definition, given your null result, if there is an effect present of a
>given size, you didn't have sufficient power to detect it.
>
>cheers,
>-MH
>
>
>> Dear FSLers,
>>
>>
>> We compared the GM, volumetric abnormalities between 3 groups of subjects
>> in an ANOVA design using TFCE based thresholding, at .05. However we did
>> not find any differences between two of the 3 groups. We are now trying to
>> understand if this was due to our sample sizes.
>>
>> The previous posts on this list were not helpful, probably bec of my level
>> of knowledge in statistics.
>>
>>
>> Could you please guide me to do this power analysis ?
>>
>> Thank you,
>>
>> Sinan
>>
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