Chapter 11 Basic usability for interactive visualizations
move earlier?
How to measure usability?
MEELS
- Memorability
- Efficiency
- Errors
- Learnability
- Satisfaction
https://www.nngroup.com/articles/usability-101-introduction-to-usability/
Three independent measures * Accuracy (Percent Correct) * Time to Complete Each Scenario * Satisfaction
https://www.usability.gov/get-involved/blog/2006/03/complete-picture-with-usability-testing.html
11.1 What do users want to do with a dashboard
Typical User Performance Tasks
Retrieve absolute value: “What was the price of barrel of oil in February 2015?”
Retrieve ratio value: “About what is the ratio of the cost of a sandwich to the total cost of room service in Seattle?”
Find extremum: “In which country is the average internet speed the fastest?”
Make comparisons: “Which metro system has more ridership?”
Find correlations/trends: “What is the relationship between the height and weight of these individuals?”
http://dx.doi.org/10.1109/TVCG.2016.2598920
Dashboard activities
- Navigation between pages
- Customizing page content with searches, filters
- Locating relevant content
- Reading content and charts
Tasks for dashboards * Check that things are going ok * Check that a process had completed * Troubleshoot a problem * Support a tactical decision * Decide where to allocate resources * Try to better understand a complex system
http://www.jeromecukier.net/2015/02/07/dashboards-as-products/
11.2 How to Test a Dashboard
Different things to test
- Tone and style
- Comprehension
- Usefulness
- Readability
- Organization
- Navigation
- Interaction
- Engagement and influence
https://www.uxmatters.com/mt/archives/2009/12/testing-content-concepts.php
11.2.1 Preliminary Questions
- Can act as a warm up before scenarios/tasks
- Good for first impressions
- Avoid leading, closed, or vague questions
https://www.nngroup.com/articles/leading-questions/
Sample Preliminary Questions
Ask: “Have you heard of [site]?” ____Yes ____No
If yes, ask: “Tell me what you know about them.”
Bring the test participant to [site]. Ask: “Just from looking at this site, what kinds of information do you think you could get from this site? Please be specific.”
Ask: “Who do you think this site is designed for? Why?” (Probe: public, health professionals, etc.)
https://www.usability.gov/how-to-and-tools/resources/templates/what-testnote-takers-guide.html
11.2.2 5-second test for first impressions
Evaluating memorability, style, satisfaction
Show the page for only 5 seconds, then ask (e.g.): * “What is the purpose of the page?” * “What are the main elements you can recall?” * “Who do you think the intended audience is?” * “Did the design/brand appear trustworthy?” * “What was your impression of the design?”
11.2.3 Think-aloud Scenarios
Evaluating efficiency, errors, learnability
Present 3-5 Think-Aloud Scenarios
Specific tasks you designed the visualization for, based on initial user testing * Make the task realistic * Make the task actionable * Avoid giving clues and describing the steps
https://www.nngroup.com/articles/thinking-aloud-the-1-usability-tool/ https://www.nngroup.com/articles/task-scenarios-usability-testing/
“First click” testing as a variation
Describe scenario, then ask what participant would click on first https://www.usability.gov/how-to-and-tools/methods/first-click-testing.html
11.2.4 Closing Questions
Evaluating memorability, style, satisfaction
- What is your overall impression to [site]?
- What is your impression of the search capability?
- Do you feel this site is current? Why?
- What did you like best about the site?
- What did you like least about the site?
https://www.usability.gov/how-to-and-tools/resources/templates/what-testnote-takers-guide.html
One question to rule them all
Single Ease Question (SEQ)
Overall, this task was?
Very Difficult…Very Easy (7-point scale)