Comparing two designs (or anything else!) using paired sample T-tests - Improving the User Experience through Practical Data Analytics - page 89

discussed how to interpret the results. We ended the chapter with an optional detailed
discussion of why independent samples and paired samples must be analyzed differently
to arrive at correct results.
3.8 EXERCISE
1. Consider the case of satisfaction with a design in a scenario where 20 people
each experience two different designs (i.e., paired data). Test whether the aver-
age satisfaction is the same for both designs. Data for the satisfaction for each
design are in data iles in Excel (ile name: Chapter 3.Exercise 1.data) and in
SPSS (ile name: Chapter 3..Exercise 1.data).The output in Excel is on sheet 2.
In SPSS the output is in a ile (ile name: Chapter 3..Exercise 1.output).
A Word ile (ile name: Chapter 3..Exercise 1.discussion) is also provided, which
discusses the results.
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Lewis, J.R., 1994. Sample sizes for usability studies: Additional considerations. Human
Factors 36, 368-378.
Nielsen, J., Landauer, T.K., 1993. A mathematical model of the inding of usability problems.
In: Proceedings of ACM INTERCHI'93 Conference. ACM Press, Amsterdam, Netherlands,
pp. 206-213.
Virzi, R.A., 1992. Reining the test phase of usability evaluation: how many subjects is
enough? Human Factors: The Journal of the Human Factors and Ergonomics Society 34
(4), 457-468.