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An introduction to usability

An introduction to usability. Dr. Simeon Keates. Usability…. Q – What makes a “good” product? Q – What makes a “better” product? Q – How do you define “usability” and “accessibility”? Q – When should usability be considered in the design process?

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An introduction to usability

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  1. An introduction to usability Dr. Simeon Keates

  2. Usability… • Q – What makes a “good” product? • Q – What makes a “better” product? • Q – How do you define “usability” and “accessibility”? • Q – When should usability be considered in the design process? • Q – When is a product OK to release to customers? • Q – How do you define “sufficiently” usable?

  3. How do you define “usability”? • Suggestions? Typical answers: • “The ability to get to a product’s functionality” • “The ability to use a product successfully” • “Intuitiveness / ease of learning” • “Ease of use” • “User friendliness” We need something more concrete… … and usable …

  4. How do you define “usability”? (source: ISO 9241-11) ISO 9241 definition: • “The effectiveness, efficiencyand satisfactionwith which specified users achieve specified goals in particular environments” • effectiveness: the accuracy and completeness with which specified users can achieve specified goals in particular environments • efficiency: the resources expended in relation to the accuracy and completeness of goals achieved • satisfaction: the comfort and acceptability of the work system to its users and other people affected by its use

  5. Measuring usability (source: Patrick Jordan “An introduction to usability) Effectiveness: the extent to which a goal or task is achieved • Task completion: • How much got done? • Quality of output: • Was what got done any good?

  6. Measuring usability (source: Patrick Jordan “An introduction to usability) Efficiency: the amount of effort to accomplish a goal • Deviations from the critical (i.e. shortest) path: • How much did the user wander? • Error rate: • How often did the user make a mistake? How “bad” were the mistakes? • [More on this on Friday] • Time on task: • How long did it take? • Mental workload: • How hard did the user have to think?

  7. Measuring usability (source: Patrick Jordan “An introduction to usability) Satisfaction: the level of comfort that the user feels when using a product and how acceptable the product is to users as a vehicle for achieving their goals • Qualitative attitude analysis: • Did you like it? • Quantitative attitude analysis: • How much did you like it? (e.g. benchmarking)

  8. Typical usability considerations (source: Wikipedia “Usability” entry) • Can users “easily” accomplish their intended tasks? • For example, can users accomplish intended tasks at their intended speed? • How much training do users need? • What documentation or other supporting materials are available to help the user? • Can users find the solutions they seek in these materials? • What and how many errors do users make when interacting with the product? • Can the user recover from errors? What do users have to do to recover from errors? Does the product help users recover from errors? • For example, does software present comprehensible, informative, non-threatening error messages? • Are there provisions for meeting the special needs of users with disabilities? (Accessibility)

  9. Getting started…The purpose of “design”

  10. What are we aiming for? (Source: Jakob Nielsen “Usability Engineering”) Acceptability Practical acceptability • Utility • Usability

  11. What is the aim of design? – An example

  12. The functional choice…

  13. The aspirational choice…

  14. What are we aiming for? (Source: Jakob Nielsen “Usability Engineering”) Acceptability Practical acceptabilitySocial acceptability Utility Aesthetics Usability Desirability Branding

  15. Designing an acceptable interface

  16. What is a good interface? • Acceptable by the intended user group • (Jakob Nielsen “Usability Engineering”) Need to define: • What is the intendedusergroup? • What is acceptable?

  17. Who are the users? • Often defined by marketing • “Target” users… • Defined by socio-economic factors • For usability can (should) take a broader view • Defined by user needs and wants • i.e. users who should be able to use the product • Accessibility takes an even broader view

  18. What is a good interface? • Acceptable by the intended user group • (Jakob Nielsen “Usability Engineering”) Need to define: • What is the intendedusergroup? • What is acceptable?

  19. Designing an acceptable interface – Social acceptability • Desirability • Do I want this? • Aesthetics • Does it look nice? Does it please my senses? • Branding • Does this product have values that I identify with? • Style • Does this product match my personal sense of style?

  20. Designing an acceptable interface - Practical acceptability • Utility (a.k.a functionality) • Does it do what it is supposed to? • Usability • Can the user get to the functionality? • Accessibility • Can all users get to the functionality?

  21. Where do problems arise? • Focusing on technical development issues • Focusing on deadlines • Not understanding the users • Not focusing on the users Designers designing for themselves (Alan Cooper “The inmates are running the asylum”)

  22. A better approach to designing for usability…

  23. The fundamental stages of design • STAGE 1 - define the problem • STAGE 2 - develop a solution • STAGE 3 - evaluate the solution user wants/needs system requirements develop a usable system for “all” users verify/validate for all users

  24. Designing for usability – Reliability and validity Reliability • How repeatable is your data collection? • Have you done the thing “right” ? Validity • Has your data collection answered your question? • Have you done the “right” thing?

  25. Understanding the task • Good usability requires a good understanding of both the users and the task/goal • For example, at an ATM: • User asked “Which account to withdraw cash from?” • User reads the prompt (vision, cognitive / learning) • Finds the available buttons to choose between (vision, maybe motor) • Identifies the buttons (vision, cognitive / learning / memory) • Decides which one to press (cognitive / learning) • Activates it (motor, maybe vision)

  26. Exercise 1 – Task analysis • What are the steps in making a cup of tea?

  27. Methods for assisting the design of usable interfaces • Virtually all user-centred (or user sensitive) design methods • ONLY IF the correct users are chosen

  28. Knowing the users – I • Q – What affects how acceptable an interface is to person? • A – How it corresponds to their: • Capabilities • Experiences • Education • Expectations • Attitudes

  29. Knowing the users – II • Q – How do users differ from other users? • A – By their: • Capabilities • Experiences • Education • Expectations • Attitudes

  30. Users… • Who are they? • Varies by project • What capabilities/characteristics? • Varies by project • How many? • Varies by project • How to report the results? • Varies by project

  31. “Standard” usability methods • Surveys • Interviews • Focus groups • Ethnographic studies • Performance estimates • User trials

  32. Input Output Exercise 2:Card-sorting for the Personal Information Point

  33. Exercise 2 – Background • The PIP has 6 buttons for input • Those buttons can be used for any purpose you choose • The LCD screen will display the output only • i.e. no touch input

  34. Exercise 2 – Details • Design the PIP to support the sale of computers • You have been given a list of computer models in your handout • Research the models • Design a set of paper prototypes for how that information can be displayed on the PIP

  35. Exercise 2 – Questions to answer • What do you think is the minimum number of button presses needed to help a novice user decide which product to invest in? • What do you think is the maximum number of button presses? • What do you think is the expected number of button presses? • Do you think that this is the “best” possible design? If not, propose an alternative design – and calculate the minimum, maximum and expected number of clicks.

  36. Exercise 2 – Discussion • Variety of possible design decisions and choices • Clustering of products • Scroll bars • Simple list • Where to put the back button?

  37. Back button… Product 1 Product 4 Product 2 Product 5 Here? Product 3 <Back

  38. Back button… Product 1 Product 3 Product 2 Product 4 Or here? Product 5 <Back

  39. Calculating the number of button presses

  40. Possible categorisations for the computers • Price • Cheap, average, expensive • Brand • Sony, Samsung, etc. • OS • Mac or PC • Screen size • 8”, 10”, etc. • Purpose • Netbook or laptop

  41. Different information architecture approaches • Simple lists • Simple list • Better list • Even better list • Scrolling • Product clusters • Directed search

  42. Calculating the number of button presses Assumptions: • No errors are made • User only selects the particular product of interest • No exploration • Random likelihood of product choice What should we report? • Easy: minimum and maximum number of button presses • Slightly harder: Average number of button presses • Harder (but more useful): Expected number of button presses

  43. How many button presses? – Ultra-simple list design Product 1 Product 4 Product 2 Product 5 Product 3 Next page>

  44. How many button presses? – Ultra-simple list design Product 6 Product 9 Product 7 Product 10 Product 8 Next page>

  45. How many button presses? – Ultra-simple list design • Total number of screens = 21 products ÷ 5 products per screen = 5 screens total • Minimum of 1 button press, maximum of 5 • Average = 3 button presses

  46. How many button presses? – Ultra-simple list design Assuming a random likelihood of product choice: • 5 in 21 chance of 1 button press [i.e. 23.8%] • 5 in 21 chance of 2 button presses • 5 in 21 chance of 3 button presses • 5 in 21 chance of 4 button presses • 1 in 21 chance of 5 button presses • E(number_of_button_presses) = p(product being on page 1) * 1 + p (product on page 2) * 2 + p (page 3) * 3 + p(page 4) * 4 + p(page 5) * 5 • Actual expected value = 2.6 button presses

  47. How many button presses? – Ultra-simple list design • Do we believe this calculation? • What problems can you see with it? Answer: No Answer: Navigation is very naïve (only moves forward) No error tolerance No support for exploration

  48. How many button presses? – A better simple list design Product 1 Product 3 Product 2 Product 4 <Previous page Next page>

  49. How many button presses? – A better simple list design Product 5 Product 7 Product 6 Product 8 <Previous page Next page>

  50. How many button presses? – A better simple list design • Total number of screens = 21 products ÷ 4 products per screen = 6 screens total • Minimum of 1 button press, maximum of 6 • Average = 3.5 button presses

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