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Analyzing quantitative usability data

Typically, analyzing data from usability testing begins with using “descriptive statistics.” 

The most common descriptive statistic for usability testing is frequency counting. 
Most quantitative data collection methods for usability testing (e.g., post surveys, recording procedures, think alouds, debriefing, etc) allow you to count the frequency of user behavior, such as the number (or percentage) of errors that occur on tasks and the number of users who successfully perform tasks.   

Example

Post-survey question – “Overall, do you believe this technology improved your knowledge of assessing instruction?”

Response Frequency Percentage  

Strongly disagree

0

0%

0% Disagree

Disagree

0

0%

Neutral

3

30%

30% Neutral

Agree

6

60%

70% Agree

Strongly agree

1

10%

Total

10

100%

Typical user behavior is another descriptive statistic commonly used.  Generally, this is used for determining the average (mean) of a behavior (e.g. time taken) for a certain task. 

Example

From test monitor (data logging sheets) –
Task 4c: “Participants will find web page on how to write survey questions for assess teaching”

Participant Time completed
(min:secs)
Errors

Participant 1

1:30

0

Participant 2

4:20

5

Participant 3

5:20

3

Participant 4

4:10

3

Participant 5

3:32

4

Mean

3:46

3

For greater usefulness, both of these examples should include text explanations to help readers interpret the quantitative results. 

Page last updated: Sep 21 2011
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