[Sigia-l] Card Sorting: How Many Users to Test

[Eric Scheid]

ahh ... surely there's something controversial in Jakob's latest AlertBox...

http://www.useit.com/alertbox/20040719.html

> You must test fifteen users to reach a correlation of 0.90, which is a more
> comfortable place to stop. After fifteen users, diminishing returns set in and
> correlations increase very little: testing thirty people gives a correlation
> of 0.95 -- certainly better, but usually not worth twice the money. There are
> hardly any improvements from going beyond thirty users: you have to test sixty
> people to reach 0.98, and doing so is definitely wasteful.