Sample Size and Power Analysis Calculator

You have found the Longbow power/sample size calculator, a free service from Loyalty Builders to help marketers decide if they can rely on results of their marketing test (the power calculation) or how big their sample size should be for accurate results. Calculating sample size or power is complex; we are trying to make the task simpler. There are several variables involved. The definitions and roles of these variables are discussed, along with multiple examples, in a document on the Longbow Help Center.

In keeping with the Longbow tag line (“We do the math. You do the marketing.”) this is a tool designed for marketers, not statisticians. Consequently we have made some decisions and assumptions to appropriately tailor this calculator, for example setting the default value for significance at 0.05 (but you can change it too). Also, estimating standard deviation is not easy for marketers, so we offer an approximate way for us to make an estimate for you. The bottom line is that our lawyers insist on the following caveat:

The results from this calculator are based on estimated measures of variation. Your data may vary significantly, making our results inaccurate. Loyalty Builders assumes no responsibility for decisions based on the results of this calculator. Your use of this calculator means that you accept this disclaimer.

If you accept this disclaimer, click on the link below to move on to the calculator itself.  Send feedback and questions to support@loyaltybuilders.com. We’d like to hear from you, and will do our best to answer your questions.

Sample Size and Power Analysis Calculator