Hint: Use this calculator to estimate the Sample Size for a given Margin of Error (Acceptable Difference) for continuous data (mean). E.g. You want to check the average time for a transaction and your research shows a standard deviation of 2.5 in the transaction time. You are okay if your survey result is ±5% of actual mean. How many transactions will you monitor to be 95% sure that the average time is correct?

Confidence Level

In the above example it is 95%

90%

95%

99%

99.9%

Known Standard Deviation

This is the historic or the researched standard deviation. In the above example, it is 2.5

Acceptable Difference %

or the Margin of Error. In above example it is 5%. Just enter 5