O'Reilly logo

Quantifying the User Experience, 2nd Edition by James R Lewis, Jeff Sauro

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Chapter 4

Did we meet or exceed our goal?

Abstract

This chapter covers methods for determining whether a design has met or exceeded a specific goal. The statistical test you use for completion rates depends on the sample size: A sample size is considered small unless you have more than 15 successes and 15 failures. For determining whether a certain percentage of users can complete a task for small sample sizes use the midprobability from the binomial distribution. For determining whether a certain percentage of users can complete a task for large sample sizes use the normal approximation to the binomial. You can always convert continuous rating scale data into discrete-binary data and test a percentage that agrees with a statement, but in so doing, ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required