Well Tracy

optimum sample size is dependent on various factors.

Have you looked into the tools available for calculating sample sizes?

For xample:

http://epitools.ausvet.com.au/content.php?page=case-controlSS

or

http://osse.bii.a-star.edu.sg/

There is also quite a wealth of literature and  more general manuscript that might be helpful:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3775042/

Probably, you are interested in a more specific solution for your questions? The pros and cons of a particular power, whatever....? Then, please specify what your ideas and thoughts are. That will make answers more suitable to your needs.

good luck!

SR

Hi,

Your question on sample size calcuation for fMRI studies.  Kindly see the following links:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427872/

http://www.dovepress.com/getfile.php?fileID=12772

http://fmri.wfubmc.edu/userfiles/file/PowerSampleSizeCalculation/PDF/PowerMapPaper.pdf

http://rsl.stanford.edu/glover/papers/desmond_glover_power.pdf

I give a straightforward tutorial in the linked paper. This may help you think about what you need

Article Sample Size in Disease Management Program Evaluation: The Ch...

Thanks! Im familiar with sample size calculation however not sure what to use as the outcome measure for fMRI

That wasn't the question you originally asked. What outcome are you looking at for fMRI? You would know this answer better than we would. You didn't give us any information about your study, so we really can't give you an adequate response

Hi,

Although there are nice articles above, I think this one addresses exactly your question:

http://dx.doi.org/10.1016/j.neuroimage.2004.02.005