COMP 388/441 HCI: 01 - Usability of Interactive Systems. 01- Usability of Interactive Systems

Transcription

1 01- Usability of Interactive Systems

2 HCI: General Motivation/Overview Early computers were only usable by experts with strong technical knowledge and not by average users (with limited technical knowledge) UI designers combine technical knowledge with sensitivity to human needs and capacities Consequently: HCI is strongly interdisciplinary HCI is a combination of: Psychology, Computer Science, Graphic Design, Human Factors/Ergonomics, Anthropology, Sociology, Economy, Law, etc.

3 Lecture 01 - Overview Usability Goals/Requirements What to do? Introduces 4 (sets of) goals that should be pursued when developing UIs (e.g., ascertain users needs, promote consistency, etc.) Usability Measures How to measure success? Introduces some usability measures that help to determine the effectiveness of the product in regard to usability (e.g., time to learn, rate of errors, etc.) Usability Motivation Why care at all? Provides some motivational aspects for HCI (e.g., life critical systems, sociotechnical systems, etc.) Universal Usability How to cope with diversity of users? Discusses challenges that face UI designers in regard to diverse user groups/communities (e.g., different physical abilities, cultural differences, etc.)

4 Usability Goals/Requirements

5 Usability Goals/Requirements Overview When developing UIs you need to focus on quality features such as usability, universality, usefulness UI designers must have a thorough understanding of the diverse communities of users and the tasks that they need to accomplish Explicit goals are needed that help to ensure usability: Ascertain users needs Ensure proper reliability Promote appropriate standardization, integration, consistency, and portability Complete projects on schedule and within budget

6 Usability Goals/Requirements (1) Ascertain users needs Users needs the tasks and subtask that the user needs to carry out when using the UI/product Perform a task analysis: This will help to discover also infrequent and exceptional tasks Add appropriate extent of functionality (inadequate vs. clutter); possibly hide infrequently used functions but make sure that advanced users can access them effortlessly if required (e.g., calculator with different views for basic and scientific use) Note: The target audience/user community is an influential factor in regard to the extent of functionality that you should offer

7 Usability Goals/Requirements (2) Ensure proper reliability All actions that the user takes must reflect appropriate results; presented information must be accurate If you do not provide this kind of reliability users will quickly loose trust in your application and stop using it It is important to use hardware, software, and/or architectures that support this kind of reliability (e.g., high availability in networked applications) Finally, consider privacy, security, data integrity, and the possibility of malicious tampering

8 Usability Goals/Requirements (3) Promote appropriate standardization Standardization use of common UI features across multiple applications Especially important with increasing number of available applications and users Standardization can be immensely beneficial Reduced learning time ( e.g., lower costs for businesses) Reduced error probability and frequency Reduced development time/costs Example for desktop environments: Apple Computers, Microsoft Windows Example in regard to human factors: ISO 9241: Ergonomics Requirements for Office Work with Visual Display Terminals

9 Usability Goals/Requirements (3) Promote appropriate integration Examples: Unix piping -concept enables different applications to work together (e.g., who lpr); compatibility across MS Office applications allows easy information exchange You should consider similarities/relations in applications and make such exchange possible Even tough integration does not immediately appear to be UI-related it is very important in this context as it influences the functionality and usability of your application It should be part of the UI designer s responsibility to recognize such potentials and communicate it to other project members

10 Usability Goals/Requirements (3) Promote appropriate consistency Consistency use of common action sequences, terms (e.g., cancel vs. abort ), colors, font sizes, button sizes, data formats, etc. 3 scopes of consistency: Be consistent within one application Be consistent within related applications/application packages Be consistent within different versions of one application

11 Usability Goals/Requirements (3) Promote appropriate portability Portability the potential of sharing an interface and the data that is associated with it between multiple platforms (i.e., software/hardware) Some challenges are different display sizes, resolutions, interaction devices, web-browser features, data formats (e.g., PDF vs. WORD-doc ) Always assume that your UI may be used in various heterogeneous environments Sometimes the kind of target system is governed by customer requirements (e.g., an Intranet application where all users are required to use IE 5.5) Use GUI Frameworks/APIs (e.g., Java Swing) and data formats (e.g., XML, PDF) that support portability

12 Usability Goals/Requirements (4) Complete projects on schedule and within budget Certainly a general goal for all software projects Sometimes UI designers forget about this goal, however it is as crucial to UI design as it is to other parts of the software development process Every delay or increase in costs will affect your project in one way or the other (e.g., the client switches to another product)

13 Usability Measures

14 Usability Measures Overview Assuming that the discussed usability goals are known and applied, how can we determine that we succeeded, how can we measure usability? Use a set of well defined criteria/measures that help to determine the effectiveness and usability of your UI Note: This process varies based on different user communities, user expectations and tasks This observation requires to follow 2 steps in your evaluation process 1. Determine your communities and the set of tasks that you need to benchmark 2. Define precise objectives for each task and community. This will guide the evaluation process

15 Usability Measures 5 Aspects 1. Time to learn How long does it take a typical member of your user community to learn how to use the UI in order to perform the defined tasks? 2. Speed of performance How long does it take to perform the benchmark tests? 3. Rate of errors by users How many and what kind of errors do users make in carrying out the benchmark tasks? (Note: This is related to speed of performance ) 4. Retention over time How well do users maintain their knowledge of how to use your UI? (Note: This is related to time to learn ) 5. Subjective satisfaction How much did users like the UI or certain aspects of it?

16 Usability Measures Conclusion Commonly it is tough to perform equally well in all of the 5 objectives; there are trade-offs Example: The use of shortcuts or abbreviations increases the time to learn but also increases the speed of performance You need to determine which of the 5 measures are most important for your specific project and community Do not hesitate to communicate specific UI design goals/objectives and the respective trade-offs to product managers and/or clients (e.g., if speed of performance is crucial, emphasize that the operational productivity of the UI will be better in favor of possibly longer learning times)

17 Usability Motivation

18 Usability Motivation Overview Many current UIs are still designed poorly However, well-designed UIs can bring great benefits to the user and other stakeholders There are 5 distinct groups of systems/applications that each have distinct characteristics and that each provoke specific motivational aspects for usability 1. Life-critical systems 2. Industrial and commercial applications 3. Office, home and entertainment applications 4. Exploratory, creative and collaborative applications 5. Sociotechnical systems

19 Usability Motivation Life-Critical Systems Example: Air-traffic control, medical instruments, nuclear reactor control, etc. Characteristics High costs are expected and accepted High reliability and effectiveness is a must Time-to-learn is commonly high High speed of performance and low error rates are crucial Subjective satisfaction is of less importance (we deal with well-motivated professionals) Retention is obtained by frequent use and intensive practice

20 Usability Motivation Industrial and Commercial Applications Example: Banking software, inventory management systems, human resource management software (e.g, SAP, PeopleSoft), etc. Characteristics Costs are a very important factor Reliability and operational efficiency is important but not as crucial as it is with life-critical systems Time-to-learn should be low (as it lowers the costs) Speed of performance needs to be high (faster operating speed potentially increases the organization s profit) However, error rates should be low (trade-off with speed) Subjective satisfaction is of less concern After an initial training period, retention is obtained by very frequent use

21 Usability Motivation Office, Home and Entertainment Applications Example: , word processing, games, mobile phone applications, etc. Characteristics Should be easy to learn Should have low error rates Should be produced at low costs (due to high competition) Subjective satisfaction is important Retention should be supported by use of easy-to-remember procedures and online-help Some critical issues: High competition, commonly quick user frustration, use frequencies sometimes very low, very diverse communities, choosing adequate extent of functionality is difficult

22 Usability Motivation Exploratory, Creative and Collaborative Applications Examples: WWW, search engines, music composition systems, architectural design systems, Wikis, Blogs, Google Documents, etc. Characteristics User is commonly familiar with the task domain Motivation is high Expectations are high Usage-rate: occasional to frequent Challenge: It is hard to describe/define benchmark tests because of the exploratory nature of these applications; in general: such applications are difficult to design and evaluate!

23 Usability Motivation Sociotechnical Systems complex systems that involve many people, possibly over a long period of time Example: Voting System, ID Verification System Such applications are often created by governmental organizations Characteristics Trust, privacy, and responsibility issues are very important It is also important to reduce chances of malicious tampering or provision of incorrect information Need to provide appropriate feedback (e.g., voting system) Users may be extremely diverse Ease of learning is crucial (we commonly deal with many novice and inexperienced users)

24 Universal Usability

25 Universal Usability Overview Deals with diversity of users (e.g, physical abilities, cultural aspects, personal differences, etc.) but also with diversity of hard- und software systems Diversity is accompanied by a variety of challenges 8 important user groups/issues 1. Physical abilities/physical workplaces 2. Cognitive and perceptual abilities 3. Personal differences 4. Cultural and international diversity 5. Users with disabilities 6. Senior citizens 7. Children 8. Differences in soft- and hardware

26 Universal Usability Physical abilities/physical workplaces There is no average user (statistically there is, but not from a HCI standpoint) Users are different in their physical abilities (e.g., arm length, size of fingers, strength of vision) UI designers must either make compromises or provide different versions or possibilities for adjustment (e.g., font size increase via + ) The nature of interaction devices (they are part of the UI) is also influenced by diverse physical abilities and workplaces (e.g., keyboard design)

27 Universal Usability Cognitive and perceptual abilities You must understand the cognitive and perceptual abilities of your target group/user community A classification of human cognitive processes provides the UI designer with a framework Short-term and working memory, long-term and semantic memory Problem solving and reasoning, decision making and risk management Language communication and comprehension Search, imagery, and sensory memory Learning, skill development, knowledge acquisition Other factors that affect perceptual and motor performance are, for instance, monotony and boredom, fear, anxiety, mood, and emotions Naturally, background experience and knowledge in the task domain influence the learning process and the user performance

28 Universal Usability Personal differences Different people have different preferences in using computers (e.g, DM vs. command language) The UI designer needs to understand the different personalities. This helps to design successful UIs for specific user groups Problem: It is hard to specify a taxonomy for personality types; in other words, personality is hard to classify 3 possible ways (Note: None of these is a silver bullet approach, they need to be applied with care): MBTI (Myers-Briggs Type Indicator) Big-Five-Test ( successor of the MBTI) Studies of user behavior

29 Universal Usability Cultural and international diversity Includes issues such as race, cultural, linguistic, and ethnic backgrounds Example for cultural differences: color black vs. white as an association with death Globalization is an important factor in promoting the need for adapting UIs to different cultures etc. Some specific issues/examples: Characters, numbers, special characters (e.g., ß, ) Horizontal right-to-left and left-to-right vs. vertical top-tobottom reading Date and time formats (e.g., dd.mm.yyyy vs. mm/dd/yyyy) Address formats (e.g., ZIP city vs. city, ZIP ) Numeric and currency formats (e.g.,. vs., as decimal delimiter)

30 Universal Usability Users with disabilities In the U.S., federal agencies are required to ensure access to IT by employees and the public. This includes an emphasis on users with disabilities Examples: Vision impaired (provide different font size & color, screen size, resolution, offer text-to-speach conversion, voice over) Hearing impaired (provide alternatives, for instance, text) Mobility impaired (provide different kinds of interaction devices, for instance, a virtual keyboard) It is crucial to pay attention to such issues; commonly the earlier they are recognized the less costly it will be to implement the appropriate functionality Finally: If you develop UIs for the government, it is a must to consider these issues

31 Universal Usability Senior citizens Becoming older may have a negative impact on physical, cognitive and social abilities Considering such issues in UI design is especially important as the population constantly becomes older, which implicates a shift in your target audience/user community Issues (examples): Visual and auditory acuity Speed of response/reaction Memory loss Decline in perceptual flexibility Increased difficulty in acquiring complex mental skills The good news is that many of these issues can be addressed Note: Older adults tend to be more quickly frustrated or even scared by technology; hence, it is especially important to provide a sound user experience for this age group

32 Universal Usability Children Today children use software in even very young ages The goals are commonly: educational acceleration, socialization with peers and giving the children a positive self-image Problem: There are some diverse opinions in regard to the effect of use of computers on children Also: It is important to balance the desire for challenge with parental requirements for safety (e.g., don t give penalties, be encouraging, parental control) The UI designer also needs to draw attention to the limited abilities of children (e.g., physical limitations, language limitations, low capacity for abstraction)

33 Universal Usability Differences in Soft- and Hardware Soft- and hardware is constantly changing, evolving Always look ahead, plan in advance This might slow you down, however planning ahead will most likely pay off in the future Some examples: Connection speed in networked applications Display sizes Maintenance and conversion to multiple languages

34 The End COMP 388/441 HCI: 01 - Usability of Interactive Systems Questions?