Hint: Use this calculator to estimate the Sample Size for a given Margin of Error (Acceptable Difference) for defective data (proportion). E.g. You want to survey to know how many people use Google Email and your research shows 80% of the population use it. You are okay if your survey result is 80% ±10%. How many people will you survey to be 95% sure?

Confidence Level

In the above example, it is 95%

90%

95%

99%

99.9%

Confidence Level square

Proportion

This is same as the assumed or researched proportion. In the above example it is 80%. Just enter 80

proportion one

proportion two

Acceptable Difference %

or Margin of Error. In above example it is 10%. Just enter 10