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lecture5 - ENSC 304 Human Factors and Usability Engineering...

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ENSC 304 - Human Factors and Usability Engineering Interaction Styles Performance Models Guidelines for Better Usability • Read the handout “A Day in the Life of …” • Text readings pp. 81-104 and 141-218
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ENSC 304 - Human Factors and Usability Engineering Interaction Styles • Conversational - Command line - Question and answer (Q&A) - "Natural" language • Buttons • Menus • Forms • Direct Manipulation
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ENSC 304 - Human Factors and Usability Engineering
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ENSC 304 - Human Factors and Usability Engineering
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ENSC 304 - Human Factors and Usability Engineering Conversational interaction requires a fast method of entering verbal codes, e.g. typing or voice. For a skilled typist, input may be "eyes free". Command lines • Powerful for experts • Emphasize recall over recognition Q&A • Machine controls the task sequence • Can be effective for naive or occasional users • Enforces the order of inputs Natural Language • May generate unrealistic user expectations • Used in business database applications, expert systems, etc. • Suited to voice recognition (e.g. HAL 9000)
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ENSC 304 - Human Factors and Usability Engineering Menus • Powerful for novice and occasional users • Emphasize recognition over recall • One issue is the grouping and ordering of menu items: - fixed or variable - alphabetical - by category or function - by frequency of use - by possibility for error • Another issue is width versus depth of menu structure - Miller showed that breadth is preferred over depth • Experts use menus differently than novices
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ENSC 304 - Human Factors and Usability Engineering Type of Menus • Permanent (as in assignment 2) • Pull-down, pull-up (most common) • Pop-up (at location of cursor) • Hybrid (at location of menu title) • Toolglass (transparent pop-up) • Pie or radial (coded by direction of movement) • Marking menus (allow novice to expert transition, self-revealing)
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ENSC 304 - Human Factors and Usability Engineering Menu Layout The menu covers N items (terminal nodes) in total The breadth of each menu display is b • Selection time from b items is st • Choice time after viewing each display is ct • Movement time for each menu display (worst case) is mt • Activities are sequential (Hick-Hyman law, Fitts' law)
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ENSC 304 - Human Factors and Usability Engineering st = ct + mt st = k 1 + c 1 log 2 2 b + k 2 + c 2 log 2 2 A W A W = b st = k 1 + c 1 log 2 2 b + k 2 + c 2 log 2 2 b st = k + c log 2 2 b Note there are log b N steps to make a selection: T = log b N ! st T = log b N ! k + c log 2 2 b ( ) T = k log b N + c (log b N ! log 2 2 b ) T = k log b N + c log 2 2 N Menu Layout
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ENSC 304 - Human Factors and Usability Engineering Menu Layout Total time T decreases as b increases, since N is constant.
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