Candice’s CornerApril 3rd, 2014

Statistics for HCI

• The important thing to remember is that statistics are another way to describe your research; they are not a magical crystal ball that spouts objective truth.• Today, we will cover two ways you may chose to use

statistics:•Descriptive statistics (small or large sample size); Summarize the Sample• Inferential statistics (usually larger sample size); Learn more about the population

Plan Ahead• If you think you may be interested in

using statistical measures, plan ahead and design your survey intentionally.

• Likert scales• Consistent measures• Same survey to compare across

usability testsHow do you guarantee the quality of your survey before you use it in testing?

Assumptions inform these decisions, how effective do you think users are at finding problems?

** Presentation of FactsCentral Tendency:

Average (mean) FrequencyMedian

Measures of Dispersion:Standard DeviationRange

Jakob Nielsen, www.nngroup.com

Descriptive Statistics

Have you considered ways you might present your data?

• Tables• Charts• Graphs

Radar Chart

• This is one way to display time performance or even categorical data for each user across multiple tasks.

Task 1

Task 2

Task 3Task 4

Task 5

0

20

40

User 1 User 2 User 3

Inferential StatisticsCreation of statistical propositions – Measure uncertainty

Parameter Estimates for the Population

Confidence Intervals-interval estimate of a population parameters statistical reliability.

Hypothesis Testing

Online Calculators

T-test http://

www.quantitativeskills.com/sisa/statistics/t-test.htm

http://studentsttest.com