To return to Anoop's original question, example 4.1 p108-109 of my book Cross-over Trials in Clinical Research (2nd edition), Wiley, 2002, illustrates the use of a permutation test on a cross-over trial with 12 subjects.
As regards robustness, an interesting paper is that of Donald Preece, 'T is for trouble (and textbooks): a critique of some examples of the paired-samples t-test. The Statistician, 31, 169-195 (1982).
Stephen
----- Original Message ----
From: Anoop Balachandran <[log in to unmask]>
To: [log in to unmask]
Sent: Sat, July 30, 2011 8:35:45 AM
Subject: Sample Size Question
Hi everyone,
How valid is a study which uses a sample size of 12 with a within-subject
design? Or how well can we extrapolate the conclusions to the population
studied.
I have heard that you need at least 30 per group to get a normal distribution.
That been said, I have read that even numbers approaching 10 can get you close
to a normal distribution.
The study I am talking about measures muscle fiber size using a biopsy and also
assess strength measurements.
In the exercise field, we sill use P-values so they haven't reported the
confidence intervals.
Thanks!
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