Sample Size Calculator  

You can use this sample size calculator to determine how many subjects you need to collect data from in order to get results that reflect the target population as precisely as needed.  You can also find the level of precision you have in an existing sample. 

This calculator requires Internet Explorer 3.0 or later or Netscape 3.0 or later or a compatible browser. Leave the population box blank, if the population is very large or unknown.