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User-Centered Design. CSSE 376, Software Quality Assurance Rose-Hulman Institute of Technology April 17, 2007. Outline. Reasons why products fail Usability goals Techniques Fitts' Law. Why do Products Fail? (1/2). Too much focus on the machine instead of the user
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User-Centered Design CSSE 376, Software Quality AssuranceRose-Hulman Institute of Technology April 17, 2007
Outline • Reasons why products fail • Usability goals • Techniques • Fitts' Law
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"
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
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
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
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?
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
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
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
Fitts' Law Movement Time = a + b * ID ID = log2 ( 2A / W ) A = amplitude (size of movement) W = width of target ID is the index of difficulty