The latest issue of interactions magazine, contains Dennis Wixon’s “Evaluating Usability Methods: Why the Current Literature Fails the Practitioner,”. (You have to pay to read it online, unfortunately.) Dennis is annoyed with the current debate within the usability field about “how many users?” This debate recurs every professional generation, and, as he points out, generates a lot of heat with little light.
(The debate has lately been stirred up by Jared Spool’s group, with “Eight Is Not Enough”.)
Dennis, in a remarkably exacting fashion, demonstrates how this debate is pointless, because it assumes (among other things) that the single most important criterion of usability testing is finding the greatest number of problems. He reminds us that our practices derive from engineering, not scientific method. And as such, making smart trade-offs is essential.
From the essay:
[The criterion] is short sighted in that it ignores that problems should be fixed and not just found. If we considered instead a more relevant criterion—namely, how much can we improve the product in the shortest time with the least effort?—we probably would not have asked this question, or we would have asked it in a different form, such as, “What is the best way of deploying the usability resources we have available for this development cycle in order to maximize our beneficial impact on the product?”
Dennis works with Microsoft’s Game Testing User Research, which has published a number of articles that are freely available (if, annoying, in Word .doc format).