CS 544 Discount Usability Engineering

Transcription

1 CS 544 Discount Usability Engineering Heuristic Evaluation Acknowledgement: Some of the material in these lectures is based on material prepared for similar courses by Saul Greenberg (University of Calgary), Ravin Balakrishnan (University of Toronto), James Landay (University of California at Berkeley), monica schraefel (University of Toronto), and Colin Ware (University of New Hampshire). Used with the permission of the respective original authors. 1 2 Usability Inspection is the generic name for a set of methods based on having evaluators inspect or examine usability-related aspects of a user interface usability inspectors can be usability specialists, software development consultants with special expertise, end users with task/content knowledge, or other professionals 4 ways to evaluate an interface: automatically (compute usability measures using evaluation software) empirically (usability testing with real users) formally (using models to calculate usability measures) informally (rule of thumb and general knowledge of evaluators) usability inspection is an informal evaluation

2 Discount Usability Engineering Developed by Nielson, based on using four techniques: User and task observation Scenarios Simplified thinking aloud Heuristic evaluation 3 Interface Design and Usability Engineering Goals: Articulate: who users are their key tasks Brainstorm designs Refined designs Completed designs Methods: Task centered system design Participatory design Usercentered design Evaluate Psychology of everyday things User involvement Representation & metaphors Participatory interaction Task scenario walkthrough Graphical screen design Interface guidelines Style guides Usability testing Heuristic evaluation Field testing low fidelity prototyping methods high fidelity prototyping methods Products: 4 User and task descriptions Throw-away paper prototypes Testable prototypes Alpha/beta systems or complete specification

3 Discount usability engineering Cheap no special labs or equipment needed the more careful you are, the better it gets Fast on order of 1 day to apply standard usability testing may take a week Easy to use can be taught in 2-4 hours 5 Heuristic Evaluation Developed by Jakob Nielsen Principles used to evaluate a system for usability problems Becoming very popular user involvement not required catches many design flaws Small set (3-5) of evaluators examine UI independently check for compliance with usability principles ( heuristics ) different evaluators will find different problems evaluators only communicate afterwards findings are then aggregated Can perform on working UI or on sketches 6

4 Why multiple evaluators? Every evaluator doesn t find every problem Good evaluators find both easy & hard ones 7 Heuristic Evaluation Process Evaluators go through UI several times inspect various dialogue elements compare with list of usability principles consider other principles/results that come to mind Usability principles Nielsen s heuristics supplementary list of category-specific heuristics competitive analysis & user testing of existing products Use violations to redesign/fix problems 8

5 Neilson s Heuristics (original) 9 H1-1: Simple & natural dialog H1-2: Speak the users language H1-3: Minimize users memory load H1-4: Consistency H1-5: Feedback H1-6: Clearly marked exits H1-7: Shortcuts H1-8: Precise & constructive error messages H1-9: Prevent errors H1-10: Help and documentation H2-1: Visibility of system status keep users informed about what is going on example: pay attention to response time 0.1 sec: no special indicators needed, why? 1.0 sec: user tends to lose track of data 10 sec: max. duration if user to stay focused on action for longer delays, use percent-done progress bars searching database for matches 10

6 H2-1: Visibility of system status keep users informed about what is going on Appropriate visible feedback What mode am I in now? What did I select? How is the system interpreting my actions? 11 H2-2: Match between system & real world speak the users language follow real world conventions (bad) example: Mac desktop Dragging disk to trash should delete it, not eject it! 12

7 H2-2: Match between system & real world speak the users language follow real world conventions e.g. withdrawing money from a bank machine 13 H2-3: User control & freedom exits for mistaken choices, undo, redo don t force down fixed paths How do I get out of this? 14

8 H2-3: User control & freedom exits for mistaken choices, undo, redo don t force down fixed paths Strategies: Cancel button (for dialogs waiting for user input) Universal Undo (can get back to previous state) Interrupt (especially for lengthy operations) Quit (for leaving the program at any time) Defaults (for restoring a property sheet) 15 H2-4: Consistency & standards Consistency of effects same words, commands, actions will always have the same effect in equivalent situations predictability Consistency of language and graphics same info/controls in same location on all screens/dialog boxes 16 forms follow boiler plate same visual appearance across the system (e.g. widgets) e.g. different scroll bars in a single window system! Consistency of input consistent syntax across complete system

9 H2-4: Consistency & standards These are labels with a raised appearance. Is it any surprise that people try and click on them? 17 H2-5: Error prevention try to make errors impossible modern widgets: only legal commands selected, or legal data entered 18 Provide reasonableness checks on input data on entering order for office supplies 5000 pencils is an unusually large order. Do you really want to order that many?

10 H2-6: Recognition rather than recall Computers good at remembering things, people aren t! Promote recognition over recall menus, icons, choice dialog boxes vs command lines, field formats relies on visibility of objects to the user (but less is more!) 19 H2-7: Flexibility and efficiency of use Experienced users should be able to perform frequently used operations quickly Strategies: keyboard and mouse accelerators abbreviations command completion menu shortcuts function keys double clicking vs menu selection type-ahead (entering input before the system is ready for it) navigation jumps e.g., going to window/location directly, and avoiding intermediate nodes history systems WWW: ~60% of pages are revisits 20

11 H2-7: Flexibility and efficiency of use Keyboard accelerators for menus Customizable toolbars and palettes for frequent actions Split menu, with recently used fonts on top Double-click raises toolbar dialog box 21 Double-click raises objectspecific menu Scrolling controls for pagesized increments H2-8: Aesthetic and minimalist design No irrelevant information in dialogues Bad example: 22

12 H2-9: Help users recognize, diagnose, and recover from errors error messages in plain language precisely indicate the problem constructively suggest a solution 23 Errors we make Mistakes arise from conscious deliberations that lead to an error instead of the correct solution Slips unconscious behaviour that gets misdirected en route to satisfying goal e.g. drive to store, end up in the office shows up frequently in skilled behaviour usually due to inattention often arises from similarities of actions 24

13 Types of slips Capture error frequently done activity takes charge instead of one intended occurs when common and rarer actions have same initial sequence change clothes for dinner and find oneself in bed (William James, 1890) confirm saving of a file when you don t want to delete it I can t believe I pressed Yes Types of slips Description error intended action has much in common with others that are possible usually occurs when right and wrong objects physically near each other pour juice into bowl instead of glass go jogging, come home, throw sweaty shirt in toilet instead of laundry basket move file to trash instead of to folder Loss of activation forgetting what the goal is while undergoing the sequence of actions start going to room and forget why you are going there navigating menus/dialogs and can t remember what you are looking for but continue action to remember (or go back to beginning)! Mode errors people do actions in one mode thinking they are in another refer to file that s in a different directory look for commands / menu options that are not relevant 26

14 Designing for slips General rules Prevent slips before they occur Detect and correct slips when they do occur User correction through feedback and undo Examples mode errors have as few modes as possible (preferably none) make modes highly visible capture errors instead of confirmation, make actions undoable allows reconsideration of action by user e.g. Mac trash can can be opened and deleted file taken back out loss of activation if system knows goal, make it explicit if not, allow person to see path taken description errors in icon-based interfaces, make sure icons are not too similar, check for reasonable input, etc. 27 Generic system responses for errors General idea: Forcing functions prevent / mitigate continuation of wrongful action Gag deals with errors by preventing the user from continuing eg cannot get past login screen until correct password entered Warn warn people that an unusual situation is occurring when overused, becomes an irritant e.g., audible bell alert box Do nothing illegal action just doesn t do anything user must infer what happened enter letter into a numeric-only field (key clicks ignored) put a file icon on top of another file icon (returns it to original position) 28

15 Generic system responses for errors Self-correct system guesses legal action and does it instead but leads to a problem of trust spelling corrector Lets talk about it system initiates dialog with user to come up with solution to the problem compile error brings up offending line in source code Teach me system asks user what the action was supposed to have meant action then becomes a legal one 29 H2-10: Help and documentation Help is not a replacement for bad design! Simple systems: walk up and use; minimal instructions Most other systems: feature rich some users will want to become experts rather than casual users intermediate users need reminding, plus a learning path Many users do not read manuals prefer to spend their time pursuing their task Usually used when users are in some kind of panic, need immediate help indicates need for online documentation, good search/lookup tools online help can be specific to current context paper manuals unavailable in many businesses! e.g. single copy locked away in system administrator s office Sometimes used for quick reference syntax of actions, possibilities... list of shortcuts... 30

16 Types of help Tutorial and/or getting started manuals short guides that people are likely to read when first obtaining their systems encourages exploration and getting to know the system tries to get conceptual material across and essential syntax on-line tours, exercises, and demos demonstrates very basic principles through working examples Reference manuals used mostly for detailed lookup by experts rarely introduces concepts thematically arranged on-line hypertext search / find table of contents index cross-index 31 Types of help (cont.) Reminders short reference cards expert user who just wants to check facts novice who wants to get overview of system s capabilities keyboard templates shortcuts/syntactic meanings of keys; recognition vs. recall; capabilities tooltips text over graphical items indicates their meaning or purpose 32

17 Types of help (cont.) Context-sensitive help system provides help on the interface component the user is currently working with Macintosh balloon help Microsoft What s this help brief help explaining whatever the user is pointing at on the screen Wizards walks user through typical tasks but dangerous if user gets stuck Remember the MS paperclip? 33 How to perform evaluation At least two passes for each evaluator first to get feel for flow and scope of system second to focus on specific elements If system is walk-up-and-use or evaluators are domain experts, no assistance needed otherwise might supply evaluators with scenarios Each evaluator produces list of problems explain why with reference to heuristic or other information be specific and list each problem separately 34

18 How to perform evaluation (cont.) Why separate listings for each violation? risk of repeating problematic aspect may not be possible to fix all problems 35 Where problems may be found single location in UI two or more locations that need to be compared problem with overall structure of UI something that is missing hard w/ paper prototypes so work extra hard on those note: sometimes features are implied by design docs and just haven t been implemented relax on those Severity ratings Used to allocate resources to fix problems Estimates of need for more usability efforts Combination of frequency impact persistence (one time or repeating) Should be calculated after all evals. are in Should be done independently by all judges 36

19 Severity ratings (cont). 0 - don t agree that this is a usability problem 1 - cosmetic problem 2 - minor usability problem 3 - major usability problem; important to fix 4 - usability catastrophe; imperative to fix 37 Summary Advantages the minimalist approach a few general guidelines can correct for the majority of usability problems easily remembered, easily applied with modest effort discount usability engineering cheap and fast way to inspect a system can be done by usability experts, double experts, and end users Problems: principles are more or less at the motherhood level can t be treated as a simple checklist subtleties involved in their use doesn t necessarily predict user/customers overall satisfaction may not have the same credibility as user test data (one solution to this is to include the design team and developers in the usability evaluation, as in a pluralistic walkthrough ) 38

20 Summary Research result: between 4-5 evaluators appear to be sufficient in most cases to identify 80% of total usability problems user testing and usability inspection have a large degree of nonoverlap in the usability problems they find (i.e., it pays to use both methods) Cost-benefit: usability engineering activities are often difficult to justify and carry out in a timely way, but many activities can be done quickly and cheaply, and produce useful results usability inspection turns less on what is correct than on what can be done within development constraints ultimate trade-off may be between doing no usability assessment and doing some kind 39 You now know 10 Heuristics for evaluating designs: H2-1: Visibility of system status H2-2: Match between system & real world H2-3: User control & freedom H2-4: Consistency & standards H2-5: Error prevention H2-6: Recognition rather than recall H2-7: Flexibility and efficiency of use H2-8: Aesthetic and minimalist design H2-9: Help users recognize, diagnose, and recover from errors H2-10: Help and documentation Principles can be used to systematically inspect the interface for usability problems 40

21 Readings and References BGBG (Evaluating Systems and Their User Interfaces) BGBG (Usability Inspection Methods) Optional: Neilsen, J. (1993). Usability Engineering. Read Chapter 5: Usability Heuristics,