First of all, thank you to Donald Burrill, Dennis Roberts, Paul Swank and Robert Dawson for your time in providing feedback. I have definitely learned a lot from your answers. Mostly, I have been refreshed on the idea that any truly random sample should be representative of the population it is being sampled from.
I noticed Robert's comment about people always being secretive on EDSTAT-L and will provide some details about why I have to choose only 10 from 220. I thought it would be best not to write out my research proposal originally :-) We currently have 220 children participating in an exercise intervention. My task is to estimate the stresses imposed on the hip (femoral neck) in these children during the activity. In order to estimate stresses on the hip, I need to have a computer model of the lower body of these children that includes muscle and bone geometry. In order to acquire muscle and bone geometry I need to have MRI's (magnetic resonance imaging) of the lower body for input into the model. I can currently only afford to pay for 10 MRI sessions and therefore 10 subjects. This phase of the research is mostly model development. The original question I posted was posed to me by a member of my research committee. He asked me , "How will you know whether the sub-sample differs in some way from the parent sample?"...hence my question. I now know with confidence that a random sampling should represent my parent sample. However, I don't know how to test that it is representative. I hope this clears up any questions you may have. Again, I am very appreciative of your time and feedback. Sincerely, Jeremy Bauer "Jeremy Bauer" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Good Day, > > Out of a population of 220 children, I need to randomly select 10 for use in > a pilot experiement. The selection of 10 subjects is based on financial > reasons, not on any power calculations. My question is, how do I make sure > that the subsample of 10 subjects represent my population of 220? > > The question seems basic at face value, but I'm just not comfortable with > any solutions. It is important that the subsample have similar age, height > & weight. Do I just run one t-test for each of the 3 dependent variables? > While the sample sizes are unequal, am I correct in saying that unequal > sample sizes are "ok" as long as the variances are equal? > > Any help will be very appreciated! Thank you! > > Jeremy > > . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
