1. ## sample size calculator

We want to take a sample out of 500 (population) hospitals. We don't mind having an error of 5&#37;. What is the methodology to calculate sample size? Especially, I don't understand that confidence interval of 5% or 10%. When we have already given confidence level in the calculation, why should one we confidence interval

2. uhhmm.........5% or 10% confidence interval is not valid since what is the point in selecting the sample if you're only 5% confident that it can really measure what you intend to measure......

it's 5% margin of error that you are saying.....

The other question as to what are the methodologies of getting a sample size the more common would be the Sloven's Formula just look it up in the internet ^^

and btw there are some sites that automatically solves your sample size problems though I forgot the name my bad..........

3. I can suggest the Power and Sample Size program from the Vanderbilt University (http://biostat.mc.vanderbilt.edu/twi...owerSampleSize). It is very easy to use.
You must know the probability of exposure in controls and the Odds ratio to calculate your sample size

4. What do you try to measure? Is it a proportion? Try this calculator:

http://www.dimensionresearch.com/res...mple_size.html

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