Chapter 20 Why evaluate the usability of UI designs?

Why Evaluate? Overall purpose: fold feedback into UI design Did design meet usability requirements? Quesenbery’s (2003) usability dimensions:  Effectiveness, efficiency, engagement, learnability, tolerability (error)  These can serve as types of evaluation metrics, e.g., meauure efficiency (speed) Evaluation = measurement Overall purpose: fold feedback into UI design Did design meet usability requirements? Quesenbery’s (2003) usability dimensions:  Effectiveness, efficiency, engagement, learnability, tolerability (error)  These can serve as types of evaluation metrics, e.g., meauure efficiency (speed) Evaluation = measurement

Running Example “Global Warming” interactive CD Open University info packet  Target users: high school degree (?)  Domain: distance learning  Environment: home, bus, etc. (anywhere) Problems:  Sliders lack affordance  “Running man” lacks affordance as well Not quite sure what the UI example is doing in this chapter… “Global Warming” interactive CD Open University info packet  Target users: high school degree (?)  Domain: distance learning  Environment: home, bus, etc. (anywhere) Problems:  Sliders lack affordance  “Running man” lacks affordance as well Not quite sure what the UI example is doing in this chapter…

Evaluation Activities Evaluation strategy:  What you want to achieve given time and cost constraints Evaluation plan:  Detailed design of evaluation sessions Analysis:  Crunch the numbers! (e.g., stats such as ANOVA; the Results section of a paper--facts only!) Interpretation:  Opinions for cause of results (the Discussion section of a paper) Evaluation strategy:  What you want to achieve given time and cost constraints Evaluation plan:  Detailed design of evaluation sessions Analysis:  Crunch the numbers! (e.g., stats such as ANOVA; the Results section of a paper--facts only!) Interpretation:  Opinions for cause of results (the Discussion section of a paper)

Evaluation Process See Figure 20.7 on p.433 Figure shows “feeback loop” into iterative design cycle Various techniques available:  User observations (video camera, yes yes)  UI inspections (heuristic inspection; usually by expert)  Lots of others (eye tracking of course) See Figure 20.7 on p.433 Figure shows “feeback loop” into iterative design cycle Various techniques available:  User observations (video camera, yes yes)  UI inspections (heuristic inspection; usually by expert)  Lots of others (eye tracking of course)

What happens during an evaluation session? If testing in the lab (what we’d do):  Welcome participant (why not subject?)  Explain general nature of session (without giving away all the details)  Get them to sign informed consent form  Give them instructions (prepared ahead of time---a script is a very good idea)  Get them to execute a task This is the Procedures section of a paper If testing in the lab (what we’d do):  Welcome participant (why not subject?)  Explain general nature of session (without giving away all the details)  Get them to sign informed consent form  Give them instructions (prepared ahead of time---a script is a very good idea)  Get them to execute a task This is the Procedures section of a paper