1. 1 User-Centered Design CSSE 376, Software Quality Assurance Rose-Hulman Institute of Technology April 17, 2007

2. 2 Outline Reasons why products fail Usability goals Techniques Fitts' Law

3. 3 Why do Products Fail? (1/2) Too much focus on the machine instead of the user Target audience has changed Designing usable systems is hard, but development organizations treat it as "common sense"

4. 4 Why do Products Fail? (2/2) Different teams work on different parts, and their work is not well- integrated Engineers are not good at designing user interfaces

5. 5 User-Centered Design "the practice of designing products so that users can perform required use, operation, service, and supportive tasks with a minimum of stress and maximum of efficiency" -- Wesley E. Woodson

6. 6 Usability Goals (1/2) Usefulness –Does the system enable the user to accomplish their goals? –provides motivation for use Effectiveness (ease of use) –How easily can the user accomplish tasks? –often measured quantitatively

7. 7 Usability Goals (2/2) Learnability –How long does it take a user to become competent with the system? –How long does it take to relearn? Attitude (likability) –Does the user enjoy using the system?

8. 8 Cartoon of the Day

9. 9 Techniques (1/3) Focus Groups –used before development or early on –use prototypes or surveys to measure reaction of small groups Surveys –used at any time –can be difficult to create

10. 10 Techniques (2/3) Design walk-throughs –used to test designs –may be based on use case scenarios Paper prototypes –used any time –get users' reactions to visual elements and operations

11. 11 Techniques (3/3) Expert evaluations –get an expert in usability to evaluate the system –also called "heuristic evaluation" Usability testing –collect empirical data about use –need working system

12. 12 Fitts' Law Movement Time = a + b * ID ID = log 2 ( 2A / W ) A = amplitude (size of movement) W = width of target ID is the index of difficulty