sample size calculation for sensitivity and specificity_Jeehyoung Kim_excel

file @

http://me2.do/FKXWjen6

HOW TO USE

Old test has 70% of sensitivity and 80%of specificity. New test has 80% of sensitivity and 90%of specificity.

If you want to show New test is better than old test, how many samples do you need?

In this excel sheet shows you need 142  patients and 119 normal subjects.

But in usual situation, you donot not who is patients or not. You know only prevalance. 

Then this excel sheet can calculate the next steps.

If you input 0.3 as prevalance, you can get 2 potencial numbers such as 474 and 170, but 170 is not proper.

You finally get 474 as answer and excel sheet show you "yes" as a tag for descision.