1 / 54

Lecture 5.1 Core Usability Engineering Concepts Spring 2019

A. Usability and User-Centered Design B. Usability Guidelines, Principles and Heuristics C. Levels of Usability Analysis. Lecture 5.1 Core Usability Engineering Concepts Spring 2019. A. Usability and User-Centered Design

toryb
Télécharger la présentation

Lecture 5.1 Core Usability Engineering Concepts Spring 2019

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A. Usability and User-Centered Design • B. Usability Guidelines, Principles and Heuristics • C. Levels of Usability Analysis Lecture 5.1 Core Usability Engineering Concepts Spring 2019 Lecture 5.1: Core Usability Engineering Concepts

  2. A. Usability and User-Centered Design How usability is defined and measured. How user-centered design is defined, and a set of guidelines for effective user-centered design Lecture 5.1: Core Usability Engineering Concepts

  3. What is Usability ? • There is not a unique definition for usability • Many eloquent statements in books, articles and web sites defining usability • all relevant, all acceptable Lecture 5.1: Core Usability Engineering Concepts

  4. What is Usability ? Usability means that the people who use a product can do so quickly and easily to accomplish their own tasks.  This definition rests on four points: usability means focusing on users people use products to be productive users are busy people trying to accomplish tasks users decide when a product is easy to use. • Janice (Ginny) Redish and Joseph Dumas,  A Practical Guide to Usability Testing, 1999 Lecture 5.1: Core Usability Engineering Concepts

  5. What is Usability ? • Steve Krug, Don't Make Me Think, 2000, p. 5 • [After all…] usability really just means • making sure that something works well: • …that a person of average (or even below average) ability and experience can use the thing - whether it's a web site, a fighter jet, or a revolving door - for its intended purpose without getting hopelesslyfrustrated. Lecture 5.1: Core Usability Engineering Concepts

  6. What is Usability ? • A new usability process starts by looking at who uses a product, understanding their goals and needs, and selecting the right techniques to answer the question, "How well does this product meet the usability requirements of our users?" • Whitney Quesenbery (wqusability.com) • Usability is a measurable characteristic, […] present to a greater or lesser degree, that describes how effectively a user can interact with a product. • It can also be thought of as how easy a product is to learn and how easy it is to use. • Jeff Axup, UserDesign Lecture 5.1: Core Usability Engineering Concepts

  7. What is Usability ? • Jakob Nielsen, Usability Engineering, 1993, p. 26 • It is important to realize that usability is not a single, one-dimensional property of a user interface. Usability has multiple components and is traditionally associated with these five usability attributes: learnability, efficiency, memorability, errors and satisfaction Lecture 5.1: Core Usability Engineering Concepts

  8. International Standards for Usability and UCD • ISO 9241: Ergonomics of Human System Interaction • Part -11: Guidance on usability • “[Usability refers to] the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.” • ISO 13407: Human Centered Design Processes for Interactive Systems • "Human-centered design is characterised by: the active involvement of users and a clear understanding of user and task requirements[…]” Lecture 5.1: Core Usability Engineering Concepts

  9. Remember: • Users perform usability testing on a product every time they use it • They express their verdict through either: • their continued useof the product • the lack - or serious depreciation - of it • Testing a product beforereleasing it to market, helps ensure that users’ experiences with the product will be positive. • In general: The cost in time and money spentfocusing on the user is often relatively small, especially when compared to the cost of notdoing it • Every product gets tested for usabilityeventually. Lecture 5.1: Core Usability Engineering Concepts

  10. What Does Usability Measure ? • Quality of a user's Experience (QoE/ QX) • when interacting with a product or system • web site, a software application, mobile technology, or any user-operated device • QoE: • not a single, flat property of a User Interface • is assessed by a combination of factors including: • Ease of learning  • Efficiency of use  • Memorability  • Error frequency and severity  • Subjective satisfaction Lecture 5.1: Core Usability Engineering Concepts

  11. What Does Usability Measure ? • Ease of learning- How fast a first-time user can learn the product / system interface sufficiently well to accomplish basic tasks? • Efficiency of use - How fast an experienced user can accomplish average tasks? • Memorability - If a user has used the system before, can he or she remember enough to use it effectively the next time or does the user have to start over again learning everything? • Error frequency and severity - How often do users make errors while using the system, how serious are these errors, and how do users recover from these errors? • Subjective satisfaction - How much does the user like using the system? Lecture 5.1: Core Usability Engineering Concepts

  12. What is User-Centered Design ? • An approach  for employing usability. • Structured product development methodology • Involves users throughout all stages of a product development UCD attempts to combine together • user's needs, limitations & preferences • product developer objectives • The term ‘user-centered design’ originated in Donald Norman’s research laboratory at UCSD in the 1980s and became widely used after the publication of a co-authored book entitled: User-Centered System Design: New Perspectives on Human-Computer Interaction (Norman & Draper, 1986) Lecture 5.1: Core Usability Engineering Concepts

  13. Benefits of focusing on users • while developing a system or product • Reduced training and support costs • Reduced time to learn the system • Greater efficiency of use • Reduced costs by only developing features that are needed • Reduced costs associated with changing the system later • Greater attractiveness of the system, so users will be more willing to buy and use it • Reduced number of errors caused by users (very important in case of critical systems that affect human lives – nuclear reactors, planes, medical equipment e.t.c.) Lecture 5.1: Core Usability Engineering Concepts

  14. SixKey Principles of Human-Centered Design • ISO 9241-210“Human-centered design for interactive systems” • The design must be based upon an explicit understanding of users, tasks and environments. • Users must be involved throughout designand development. • The design must be drivenand refinedby user-centered evaluation. • The design process must be iterative. • The design must address the whole user experience. • The design team must have multidisciplinary skillsand perspectives. Lecture 5.1: Core Usability Engineering Concepts

  15. B. Usability Guidelines, Design Principles and Heuristics Lecture 5.1: Core Usability Engineering Concepts

  16. Usability Guidelines • A very large (very large indeed!) number of usability guidelines exist • General design guidelines • Design Process and Evaluation, Content Organization, Optimizing the User Experience... • Interface specific guidelines • Software, Website, Electronic device… • User group specific guidelines • Profile, Age, Nationality, Accessibility ... • Platform specific guidelines • Desktop, Tablet, Mobile, Multitouch, Gestural interface… • Too many sources of guidelines - Usually come in sets - Extensive overlapping among different sets of guidelines - Several compilations of guideline sets also available Lecture 5.1: Core Usability Engineering Concepts

  17. Key websites to consider when looking for Usability Guidelines • jnd.org • Don Norman’s website on human-centered design • guidelines.usability.gov • Research-based web design & usability guidelines • usabilitynet.org •  A project funded by the European Union to provide resources and networking for usability practitioners, managers and EU projects • www.nngroup.com • Nielsen/Norman group evidence-based user experience research • usabilitygeek.com • Usability and user-experience blog • -- find many more links and resources in e-class -- Lecture 5.1: Core Usability Engineering Concepts

  18. Example: Web design guidelines compilation • “The Research-Based Web Design & Usability Guidelines” • Released by the U.S. Department of Health and Human Services (HHS). • Contains a total of 209 “official” guidelines distributed in 18 sets • Design Process and Evaluation • Optimizing the User Experience • Accessibility • Hardware and Software • The Homepage • Page Layout • Navigation • Scrolling and Paging • Headings, Titles and Labels • Links • Text Appearance • Lists • Screen-Based Controls (Widgets) • Graphics, Images, and Multimedia • Writing Web Content • Content Organization • Search • Usability Testing • PDF document available at guidelines.usability.gov Lecture 5.1: Core Usability Engineering Concepts

  19. A typical page from this document Lecture 5.1: Core Usability Engineering Concepts

  20. Design Principles / Usability Heuristics Broadusability statements that describe features of “usable” systems, guiding a developer’s design efforts • Generally considered to be a standard in best practices for high-level usability evaluation • Derived by evaluating common design problems across many systems • Heuristics are most often considered "rules of thumb" because they are so well known and understood. • Heuristic Evaluation Using a set of principles to “evaluate” a system for usability problems • User involvement not required • Catches many design flaws • Is an “Expert Review” Lecture 5.1: Core Usability Engineering Concepts

  21. Eleven General Principles for User Interface Design • Proposed by Dr. Tim Lethbridge (Univ. of Ottawa) • 1. Do not rely only just on usability guidelines – always test with users. • Usability guidelines have exceptions; you can only be confident that a user interface is good if you test it successfully with users. • 2. Ensure that the sequences of actions to achieve a task are as simple as possible. • Reduce the amount of reading and manipulation the user has to do. • Ensure the user does not have to navigate anywhere to do subsequent steps of a task. Lecture 5.1: Core Usability Engineering Concepts

  22. Eleven Usability Principles (continued) 3. Ensure that the user always knows what he or she can and should do next. Ensure that the user can figure out the affordance (what commands are available and are not available). Make the most important commands stand out. 4. Provide good feedback including effective error messages. Inform users of the progress of operations and of their location as they navigate. When something goes wrong explain the situation in adequate detail and help the user to resolve the problem Lecture 5.1: Core Usability Engineering Concepts

  23. Eleven Usability Principles (continued) • 5. Ensure that the user can always get out, go back or undo an action. • Ensure that all operations can be undone. • Ensure it is easy to navigate back to where the user came from • 6. Ensure that response time is adequate. • Users are very sensitive to slow response time • They compare your system to others. • Keep response time less than a second for most operations. • Warn users of longer delays and inform them of progress. Lecture 5.1: Core Usability Engineering Concepts

  24. Eleven Usability Principles (continued) 7. Use understandable encoding techniques. Choose encoding techniques with care. Use labels and tooltips to ensure all encoding techniques are fully understood by users. Use appropriate text styles and fonts Pay attention to colour, shading, emphasis, grouping (no flashing) 8. Ensure that the UI’s appearance is uncluttered. Avoid displaying too much information. Organize the information effectively. Lecture 5.1: Core Usability Engineering Concepts

  25. Eleven Usability Principles (continued) 9. Consider the needs of different groups of users. Accommodate people from different locales and people with disabilities. Ensure that the system is usable by both beginners and experts. 10. Provide all necessary help. Organize help well. Integrate help with the application. Ensure that the help is accurate. • 11. Be consistent. • Use similar layouts and graphic designs throughout your application. • Follow look-and-feel standards. • Consider mimicking other (successful) applications. Lecture 5.1: Core Usability Engineering Concepts

  26. Jacob Nielsen’s Ten Usability Heuristics Probably the most-used usability heuristics for user interface design Based on J. Nielsen’s work together with Rolf Molich in 1990 The final set of heuristics were released in 1994 and are still used today Visibility of system status Match between system and the real world User control and freedom Consistency and standards Error prevention Recognition rather than recall Flexibility and efficiency of use Aesthetic and minimalist design Help users recognize, diagnose, and recover from errors Help and documentation Lecture 5.1: Core Usability Engineering Concepts

  27. J. Nielsen’s Ten Usability Heuristics • 1. Visibility of system status • “What is going on?” The system should always keep users informed about what is going on, through appropriate feedback within reasonable time. Always make sure that your system communicates clearly and thoroughly with the user Lecture 5.1: Core Usability Engineering Concepts

  28. J. Nielsen’s Ten Usability Heuristics • 2. Match between system and the real world • “What are you talking about?” The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order. Make sure that user understands what your system is talking about Lecture 5.1: Core Usability Engineering Concepts

  29. J. Nielsen’s Ten Usability Heuristics • 3. User control and freedom • “Oops!” Users make mistakes, and need a clearly marked "emergency exit" to get back where want to be as fast and as simply as possible. Support Undo and Redo Always make sure that your system has a simple and efficient emergency exit to “fix” user errors Lecture 5.1: Core Usability Engineering Concepts

  30. J. Nielsen’s Ten Usability Heuristics • 4. Consistency and Standards • “Oh, I know that!” Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions. Make sure that your system has continuity across your platform Lecture 5.1: Core Usability Engineering Concepts

  31. J. Nielsen’s Ten Usability Heuristics • 5. Error Prevention • “Glad I didn’t do that!” The best designs don’t only have great error recovery but prevent users from making those errors. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action. Make sure that your system has efficient error prevention Lecture 5.1: Core Usability Engineering Concepts

  32. J. Nielsen’s Ten Usability Heuristics • 6. Recognition or Recall • “Wait, what was that already?” The system should minimize the user's memory load by making objects, actions and options visible.The user should not have to remember information from one part of the dialogue to another. Make sure that your system prioritize recognition over recall whenever appropriate Lecture 5.1: Core Usability Engineering Concepts

  33. J. Nielsen’sTen Usability Heuristics • 7. Flexibility and Efficiency of Use • “It doesn’t matter if you are an expert or a newbie” The system should incorporate accelerators, which are unseen to the novice user,but that allow the expert user to navigate faster. Always make sure that your system incorporate accelerators to facilitate the expert users without affecting novice users Lecture 5.1: Core Usability Engineering Concepts

  34. J. Nielsen’s Ten Usability Heuristics • 8. Aesthetic and minimalist design • “Wow… and WOAH” Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility Always make sure that your system is Aesthetically pleasant and Efficiently composed Lecture 5.1: Core Usability Engineering Concepts

  35. J. Nielsen’sTen Usability Heuristics • 9. Help users recognize, diagnose and recover from errors • “My Bad” Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution Always make sure that your system indicates errors and messages in plain language Lecture 5.1: Core Usability Engineering Concepts

  36. J. Nielsen’s Ten Usability Heuristics • 10. Help and Documentation • “Now I get it!” Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, listconcrete steps to be carried out, and not be too large. Always make sure that your system has appropriate documentation to help the user Lecture 5.1: Core Usability Engineering Concepts

  37. Recapitating Nielsen’s Ten Usability Heuristics Visibility of system status Match between system and the real world User control and freedom Consistency and standards Error prevention Recognition rather than recall Flexibility and efficiency of use Aesthetic and minimalist design Help users recognize, diagnose, and recover from errors Help and documentation Lecture 5.1: Core Usability Engineering Concepts

  38. C. Levels of Usability Analysis Five levels at which you can analyze usability issues Lecture 5.1: Core Usability Engineering Concepts

  39. Levels To Analyze a User Interface Usability issues may be present at different levels of a system design 1. Task Level What is to be done by the user 2. Conceptual Level Conceptual model vs. user's mental model of the system 3. Interaction Style Level Command-driven, menu-driven, direct manipulation, hypermedia 4. Interaction Element Level Windows, dialogs, commands, menus 5. Physical Element Level Screen real-estate, fonts, colors, bitmaps Lecture 5.1: Core Usability Engineering Concepts

  40. Levels To Analyze a User Interface (continued) • At each of these five levels • Design must be done • Problems can occur • Every separate usability factor must be considered at each of these five levels Lecture 5.1: Core Usability Engineering Concepts

  41. Task Level (1/3) What a user is required to do in terms of actions and/or cognitive processes to achieve a task Benefits: Provides knowledge of the tasks that the user wishes to perform. Method:Task Decomposition Decompose the high level tasks and break them down into their constituent subtasks and operations Task analysis can be a very time consuming activity if used with a high degree of detail on complex problems. ... It is possible to get caught in what is loosely termed as… Analysis Paralysis: The state of over-analyzing -or over-thinking- a situation so that a decision or action is never taken, in effect paralyzing the outcome. Lecture 5.1: Core Usability Engineering Concepts

  42. Task Level (2/3) • Task decomposition can be carried out in the following stages: • 1. Identify the task to be analyzed. • 2. Break this down into a small number subtasks (typically 4-8). • Subtasks should be specified in terms of objectives and cover the whole area of interest. • 3. Draw the subtasks as a layered diagram ensuring that it is complete. • 4. Decide upon the level of detail into which to decompose. • Remember: too much detail can cause “analysis paralysis” • 5. Continue the decomposition process, ensuring that the decompositions and numbering are consistent. • 6. Present the analysis to someone else who has not been involved in the decomposition but who knows the tasks well enough to check for consistency. Lecture 5.1: Core Usability Engineering Concepts

  43. Task Level (3/3) • Task Decomposition Example Lecture 5.1: Core Usability Engineering Concepts

  44. Conceptual Model • Mental Model • Conceptual Level (1/3) • A conceptual model is a model presented to the user, usually by a designer, researcher, or trainer, which is intended to convey the workings of the system in a manner that the user can understand. • A mental model is a model of the system that the user builds in his/her mind when presented with the above conceptual model. • The user's mental model may be based on the conceptual model he has been provided, but is probably not identical to it. Lecture 5.1: Core Usability Engineering Concepts

  45. Conceptual Level (2/3) • Desirable Properties of a Conceptual Model • Completeness • Ability of a model to abstract all real world aspects of interest through appropriate concepts and relationships • Consistency • Ability of a model • to produce an abstraction in a way that reproduces the behaviour of the real world aspect of interest in the same way throughout the model • to preserve this behaviour throughout any manipulation of the model Lecture 5.1: Core Usability Engineering Concepts

  46. Conceptual Level (3/3) • Desirable Properties of a Conceptual Model (continued) • Correctness • Ability of a model to produce an abstraction in such a way that reproduces the behaviour of the real world aspect of interest correctly • Expressiveness • Ability of a model to express all real world aspects of interest through abstraction • Conciseness • Ability of a model to produce compact abstractions of real world aspects of interest Lecture 5.1: Core Usability Engineering Concepts

  47. Interaction Style Level (1/4) • (Command Language, Forms, Menus, direct manipulation, hypermedia) • Command Language Interface (CLI) • Advantages • Flexible • Appeals to expert users • Supports creation of user-defined "scripts" or macros • Disadvandages • Retention of commands is generally very poor • Learnability of commands is very poor • Error rates are high • Non suitable for non-expert users Lecture 5.1: Core Usability Engineering Concepts

  48. Interaction Style Level (2/4) • Form Fill-in (Fill the blanks) • Advantages • Simplifiesdata entry. • Easy for user to see the options available • Fastto enter data or to make choices • Little or no trainingrequired • Shortens learning in that the fields are predefined and need only be 'recognized'. • Disadvantages • Consumes screen space • Not good for highly complex applications Lecture 5.1: Core Usability Engineering Concepts

  49. Interaction Style Level (3/4) • Menu Selection • Advantages • Extremely easy to use. Someone who has never seen the interface before can work out what to do • There are no commands to learn or remember • Affords exploration (users can "look around" in the menus for the appropriate command, unlike having to remember the name of a command and its spelling when using command language.) • Structures decision making • Disadvantages • May be slow for frequent users. • May not be suited for small graphic displays • Often can't go to the exact place you want right at the start – must navigatein submenus Lecture 5.1: Core Usability Engineering Concepts

  50. Interaction Style Level (4/4) • Direct manipulation metaphors • Advantages • Visually presents task concepts. • Easy to learn. • Errors can be avoided more easily. • Encourages exploration. • High subjective satisfaction. • Recognition memory (as opposed to recall memory) • Disadvantages • May be more difficult to programme. • Not suitable for small graphic displays. • Spatial and visual representation is not always preferable. • Metaphors can be misleading • Compact notations may better suit expert users. Lecture 5.1: Core Usability Engineering Concepts

More Related