Quantifying the User Experience, 2nd Edition

Chapter 9

Six enduring controversies in measurement and statistics

Abstract

This chapter contains discussions of six enduring controversies in measurement and statistics, specifically:

• Is it OK to average data from multipoint scales?

• Do you need to test at least 30 users?

• Should you always conduct a two-tailed test?

• Can you reject the null hypothesis when p > 0.05?

• Can you combine usability metrics into single scores?

• What if you need to run more than one test?

Because many usability practitioners deeply depend on the use of measurement and statistics to guide their design recommendations, they inherit these controversies. In this chapter we summarize both sides of each issue and discuss what we, as pragmatic usability practitioners, ...