I am planing to do one project to identified the normative data for one instrument. For the same i need to do the sample size calculation. so on what bases i have to do that calculation and what is normal sample size for that......?
The sample size will depend on how narrow a confidence interval you want for your Mean, or Ratio, or whatever you are looking at. There are different formulas depending on whether it is the mean or proportion that you are interested in.
so have a look at this
www.columbia.edu/~mvp19/RMC/M6/M6.doc
(copy and paste it in your browser)
There are various formulas to calculate sample size based upon whether the data is categorical nature or not.Based upon that there is one table to estimate the population and sample survey.
Attaching one link with the table for your reference.
http://www.research-advisors.com/tools/SampleSize.htm
Note that for normative data, confidence intervals may be much less suited than tolerance intervals, depending on your exact situation, and so sample size must be suited to obtain them (and beware that the normality assumption of the data is much more stringent than for confidence intervals)
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