Legal Research

The Rule of 5 and Usability Testing

There is a classic article by Jakob Nielsen:

Why You Only Need to Test With 5 Users

The above chart shows that there are diminishing returns after the first user's feedback. This, of course doesn't mean to stop at the first user or that every group of five is alike.

So remember Jakob's advice:

1. Test usability in three phases with five users each.
2. "You need to test additional users when a website has several highly distinct groups of users"
3. Pay attention to the core users when your site attracts a diversity of users.

And don't confuse beta / usability testing with just plain "is-it-working" testing or alpha testing.

Either way, I think this is good advice since I have seen so many projects go overboard and encouraging feedback from everyone - whether they are the target user or not.

One of the big mistakes I see is testing the site with IT and developer types in the beta phase. Admit it, they know too much and usually don't represent the average user.

Stephen

Full post as published by Stephen's Lighthouse on May 06, 2009 (boomark / email).