Restoring Confidence in Usability Results
Jeff Sauro — “Adding confidence intervals to completion rates in usability tests will temper both excessive skepticism and overstated usability findings. Confidence intervals make testing more efficient by quickly revealing unusable tasks with very small samples. Examples are detailed and downloadable calculators are available.”
June 28th, 2004 at 11:13 pm
“Here’s what you should take away from this article. First, binomial confidence intervals are a resource saving tool during formative evaluations. When refining a new feature that needs a high completion rate, say 90% for first time users, you’ll know when to reject a design earlier. If only two out of five users complete the task, there’s less than a 5% chance that the completion rate will ever be above 85%.”