Usability testing can be either qualitative or quantitative.

Qualitative usability testing focuses on collecting insights, findings, and anecdotes about how people use the product or service. Qualitative usability testing is best for discovering problems in the user experience. This form of usability testing is more common than quantitative usability testing.

Quantitative usability testing focuses on collecting metrics that describe the user experience. Two of the metrics most commonly collected in quantitative usability testing are task success and time on task. Quantitative usability testing is best for collecting benchmarks.

The number of participants needed for a usability test varies depending on the type of study. For a typical qualitative usability study of a single user group, we recommend using five participants to uncover the majority of the most common problems in the product.