The Number of Test Subjects Versus the Number of UX Test Observers
… main argument for small tests is simply return on investment: testing costs increase with each additional study participant, yet the number of findings quickly reaches the point of diminishing returns.
Sadly, most companies insist on running bigger tests.
“A big website has hundreds of features.” This is an argument for running several different tests — each focusing on a smaller set of features — not for having more users in each test. You can’t ask any individual to test more than a handful of tasks before the poor user is tired out.
As a rough summary, the goal of quant user