## Sample Size in Usability Studies: How Well Does the Math Match Reality?

###### By Jeff Sauro, PhD . September 10, 2019 . Tags: Sample Size

We’ve written extensively about how to determine the right sample size for UX studies. There isn’t one sample size that will work for all studies. The optimal sample size is based on the type of study, which can be classified into three groups: Comparison studies: Comparing metrics for statistical differences Standalone studies: Estimates a population metric (such as completion rate or perceived ease) Problem discovery: