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Problem Discovery Topics

How common are usability problems?

Jeff Sauro • September 29, 2010

Usability problem frequencies from 24 usability tests show that users are almost ten-times more likely to encounter a usability problem in a business application than a website. Users are about half as likely to encounter a problem in consumer software than a business application.[Read More]

Will five users really find 85% of all usability problems?

Jeff Sauro • May 6, 2010

The sample size formula for finding usability problems only works for a specific set of users and closed-ended tasks. With five users you will only find the more obvious problems.[Read More]

Do severe problems affect more users than trivial ones?

Jeff Sauro • March 25, 2010

While testing with five users might reveal 85% of problems that impact 31% of users (given a set of tasks and user-type), it doesn't mean you're finding 85% of the critical problems. Assume that the severity of a problem is not related to how often it occurs.[Read More]

Why you only need to test with five users (explained)

Jeff Sauro • March 8, 2010

For finding usability problems with an interface, testing with five users is fine to find problems that affect 31% to 100% of all users. If a problem is more elusive (affects fewer than 31% of users) then you need to increase your sample size. This sample size does not apply to comparing designs or generating a precise estimate of completion rates or task-times.[Read More]

If 1 of 5 users has a problem in a usability test will it impact 1% or 20% of all users?

Jeff Sauro • February 1, 2010

Insurance companies do it, drug companies do it and so should usability testers. When you observe a problem from a small sample test, it is unlikely the problem only affects a tiny percentage of users.[Read More]

Deriving a Problem Discovery Sample Size

Jeff Sauro • March 8, 2004

Shows the history and computation of deriving a sample size for discovering problems in an interface.[Read More]