Choose whether you have one group to check against a fixed target, or two groups to compare with each other, and whether you are measuring an average or a rate.

Choose one-sided only if you care about a difference in a single specific direction; choose two-sided if a difference either way would matter to you.

Enter your significance level as a decimal, such as 0.05 for a 5 percent risk of rejecting a true hypothesis. This page accepts values from 0.0001 to 0.9999, its own limit.

Enter the power you want as a decimal, such as 0.9 for a 90 percent chance of detecting a real difference. This page accepts values from 0.5 to 0.9999, its own limit.

Enter the standard deviation you expect for what you are measuring, in the same units as your difference. This page accepts values from 0.000001 to 100000, its own limit.

Enter the difference or shift you want to detect, in the same units as your standard deviation; accepted values run from 0.000001 to 100000 .

Enter the rate you expect now, as a decimal between zero and one, such as 0.1 for 10 percent. This page accepts values from 0.000001 to 0.999999, its own limit.

Enter the rate you want to detect, as a decimal between zero and one; accepted values run from 0.000001 to 0.999999 .