This article argues:
“I think we can now comfortably dump Nielsen’s suggestion to just test with 5 participants, unless you want to call yourself a behaviourist.”
I was wondering if anyone had any follow up thoughts to this - articles as current as 2016 still cite that 4-5 users are the optimal number to test with.
Additionally, I found this article: https://www.uxmatters.com/mt/archives/2016/01/how-to-determine-the-right-number-of-participants-for-usability-studies.php that also discusses issue with using only 5 participants. It states:
“When quoting statistics, we must be careful to consider the margin of error for any findings. For example, there is more to Jakob Nielsen’s oft-quoted statement, “Five participants will discover over 80% of the problems” than study teams often present. This particular statistic has a 95% confidence level and margin of error of ±18.5%, which means there is a 95% chance that a group of five participants will find between 66.5% and 100% of the problems. While some groups of five in Nielsen’s study did find nearly all of the problems, one group found only 55% of the problems. Therefore, we cannot assume that five participants are sufficient for every usability-testing situation. If there are just five participants, the results may not tell the whole story.”
And summarizes that for problem discovery, 5-10 is a good baseline and 10-12 is a good baseline for comparative.