Midterm Review

1. Midterm Review IST 331 – Design and Organization of Information Systems: User and System Principles Instructor: Mithu Bhattacharya Small revisions by Frank Ritter Spring 2011

2. Chapter 1: Why and when do we need HCD • Why study of the user is important? • Understanding the users can save lives • Understanding the user can lead to better products • Understanding the user can save money • Understanding the user does not guarantee success • Not necessary or sufficient for success • Lack of usability is sufficient for failure • When do you need to study the user? • Early in the design • Lots of users and they are important • When they are different • When lives are at risk

3. Chapter 1: Why and when do we need HCD (Contd.) • How much do you have to study the user? • Risk driven spiral design model • Evaluate all risks to success • Study user and their tasks until risk of not knowing is lower than other risks

4. Chapter 2: History of Human Centered Design • Component Fields of HCD • Human Factors • Focus on good ‘fit’ between people and their work environments • Ergonomics • Focus on ‘fit’ between people and environment by altering the environment • Human Computer Interaction • Focus on designing for people’s interaction with computer-based applications • Computer Supported Cooperative Work • Focus on people’s communication through computer-based applications

5. Chapter 2: History of Human Centered Design (Contd.) • Engineering approaches to studying human behavior • Motion study (Gillian Gilbreth) • Task could be broken into individual motions • Nature of motions determine efficiency • Time study (Frederick Taylor) • Skilled behavior determined by sequencing of motions made by operator and speed at which they were carried out • Rationalizing task into most economical sequence of actions • Maximum rate without overtiring operatives

6. Chapter 2: History of Human Centered Design (Contd.) • Hawthorne Effect • Performance improvements due to psychological factors • Not physiological

7. Chapter 2: History of Human Centered Design (Contd.) • What is Usability? • Functionality • What it does • Learnability • How easy to learn • Reliability • Complete, consistent, and robust • Efficiency • How fast is the system • Maintainability • How easy is the system to maintain and upgrade • Other characteristics • Consistency, informative feedback, explicitness, flexibility and control, error prevention and control, user guidance and support

8. Information Seeking in Context • Article - Effective Information Systems for High-performing Self-managed Teams (Barnes et al., 1996) • How self-managed teams decide what information is needed • High-performing teams communicate better in team meetings • High-performing teams have clear goals • High-performing teams do not have domineering team members

9. Information Seeking in Context (Contd.) • Factors that enhance or hinder efforts to get information • No significant difference in high and low-performing teams to the effect of openness of information system and amount of information available to team • Team’s tolerance to the 2 factors different • Tolerance correlates to team maturity level

10. The Tangled Web We Wove: A Taskonomy of WWW Use (Byrne et al., 1999)

11. The Tangled Web We Wove: A Taskonomy of WWW (Contd.) • Implications for WWW browser design • Users spend more time in reading, visual search, and waiting • Widget design could improve scrolling • Users spend long time scrolling • Improving performance of caching algorithms • Users spent long in waiting for page loading • Implications for page design • Web pages should be designed to improve readability because users read • Tradeoff between readability and scanability should be carefully evaluated • Visual search should be supported (Use of color links, underline etc.)

12. Chapter 3: User Characteristics: Bodies, Behavior, Thinking, and Groups –the ABCS • ABCS Framework • A: Anthropometric Approach • Can it be used? • Physical aspects of users and systems • Example: Users defined by their size, muscle strength etc. • B: Behavioral Approach • How is it used? • Basic behavior users can produce • Users defined by what they can perceive and what they can do • Example: Vision and hearing

13. Chapter 3: User Characteristics: Bodies, Behavior, Thinking, and Groups –the ABCS (Contd.) • C: Cognitive Approach • How do users’ think they are using it? • Considers how users think about their task and system • Example: Memories, goals, processing • S: Social Approach • What about others when using it? • Users defined by where they are – the context • Example issues on social level • Distraction by interruptions thus failing to complete safety checklist • Communication breakdown among members

14. Chapter 3: User Characteristics: Bodies, Behavior, Thinking, and Groups –the ABCS (Contd.) • Haptic Interface • Touch based interface • Hand main organ of haptic perception • Advantages • Supports users with poor vision • Supports users with poor sense of touch • Users who need additional input channel or need touch as input channel • Why haven’t Haptic Interfaces been used more? • Cost, Power , Safety (Not distal; adds safety requirements), Resistance to change, Usefulness (Visual and auditory input enough; Not good for communicating large amount of information; Problem being used to transfer information over long time period)

15. Chapter 3: User Characteristics: Bodies, Behavior, Thinking, and Groups –the ABCS (Contd.) Target d x W Time = 70 ms * Log 2 (Target distance / Target size + 0.5) (Card, Moran, and Newell, 1983) • Fitt’s Law • Time to point to an object related to distance from object and inversely related to size of object

16. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning The Stages of User Activities When Performing a Task

17. Long-term Memory Working Memory sensory buffers Visual Image Store Auditory Image Store Eyes Motor Processor Cognitive Processor Perceptual Processor Ears Fingers, etc. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) • The Model Human Processor Developed by Card, Moran & Newell (1983)

18. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) • Memory • Working memory (short term) • Small capacity • Rapid access (~ 70ms) & decay (~200 ms) • Pass to LTM after a few seconds • Primacy effect: First things in list easily remembered • Recency effect: The last items in list better remembered • Long-term memory • Huge (if not “unlimited”) • Slower access time (~100 ms) w/ little decay

19. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) • Kinds of Memory • Declarative memory • Facts or statements • What is knowledge • Explicit (Reportable) • Procedural memory • Performing procedures • How to knowledge • More robust against decay • Implicit (not reportable) • Prospective memory • To do something at future time • Prone to decay • Calendars, to do list etc

20. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) • Recognition over Recall • Recall • Info reproduced from memory • Recognition • Presentation of info provides knowledge that info has been seen before • We want to design UIs that rely on: • Recognition • Implications of Memory for Interface Design • Trying harder does not help • Ordering the presentation of objects to memory helps

21. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) • Process of Learning • Stage 1 (Cognitive): Acquire domain declarative information • Stage 2 (Associative): Declarative knowledge compiled to procedural information • Stage 3 (Skills or Tuning): Tunes knowledge that is applied

22. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) • Rasmussen’s Theory of Knowledge • Skill based control • Operator sees and acts • Little or no effects on other tasks • E.g. following a car in a lane • Rule based control • Operator applies effort to act • Attention is needed • E.g. lane changing in a car • Knowledge based control • Performance is very effortful, error prone • Used when other two levels are not applicable • E.g. Driving in an unfamiliar town

23. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) Power Law of Learning Task time on the nth trial follows a power law Time of a trial = Constant 1 (Number of trial + PP)˄-alpha + Constant 2 • Constant 1 is base time that decreases with practice; PP is previous practice on the task; alpha is between 0.1 – 0.4; Constant 2 is limiting constant • You get faster the more times you do it • Applies to skilled behavior (sensory & motor) • Does not apply to knowledge acquisition, scores, or quality

24. Chapter 6: Cognitive Capabilities: Memory, Attention, and Learning (Contd.) • Implications of Learning for Interface Design • Users learn and get faster • Learning curve may provide insights • How difficult to novices • Steep curve, system often used, initial task time not an issue • System used few times, initial task time needs to be acceptable

25. Chapter 7: Cognitive Capabilities: Human-Computer Communication • What Syntactic/Semantic Model Reveals • Mapping between three items is extremely important • Task semantics to computer semantics to computer syntax • Task semantics: Write letter • Computer semantics: Open a file, use editor, save it to disk • Computer syntax: Select menu items, key strokes for formatting • Bad mapping: Using LaTex to write letter • Aside from task semantics, must also know semantics/syntax of: • Text editor • Latex • Unix compiling and printing sequence (to typeset and print) • Relatively good mapping: Trashcan to throw away files • Must know mouse syntax of selecting and dragging • Computer semantics almost analogous to task semantics

26. Chapter 8: Cognitive Capabilities: Mental Representations and Problem Solving • What does “Mental Model” mean? • Some sort of mental representation of things in our environment • Semantic/propositional • Visual/spatial • They help us understand how people reason about different phenomena • Characteristics of MM • Incomplete, constantly evolving, not accurate representations, contains errors • Simplistic representation of complex phenomena • Set of if-then-else rules

27. Chapter 8: Cognitive Capabilities: Mental Representations and Problem Solving (Contd.) • Types of MM • Structural • Facts user has about how a certain system works • Functional • Procedural knowledge about how to use the system • Can be constructed from existing knowledge about similar domain or system

28. Chapter 8: Cognitive Capabilities: Mental Representations and Problem Solving (Contd.) • MM Limitations • Capturing and validating is hard • MMs are built on the fly • Asking about MM often modifies user’s MM • Post Completion Errors • This error arises when goals for task is completed but the goals of the subtasks are not completed • Example: Old-fashioned ATM machine • Get money before card and leave card • Goal is to withdraw money, not get card • Design suggestion • Put most important goal last so that all sub-goals are met

29. Chapter 8: Cognitive Capabilities: Mental Representations and Problem Solving (Contd.) • Simple Decision Making • Hick-Hyman law • T=a+b log2(n+1) • T=time to make a decision, n=number of options • a, b are constants that depend on the display, response mode etc. • Example: What is relative time to select from one menu of eight items vs. two menus of four items?

30. Chapter 16: Cognitive Capabilities - Cognitive Dimensions and the Gulfs • Influences on Decision Making • Confirmation Bias • We tend to look for or notice evidence that confirms our hypotheses, rather than check for contradictions • Confirmation bias can be made worse by automation, e.g., ignoring road signs while following GPS instructions • Regression to the Mean / Sample Sizes • Users tend to over generalize • Availability Bias • Users typically use memory that are easy to retrieve • Framing Effect • The way outcomes are presented influence on how users choose between alternatives • Outcomes noted in positive terms are chosen over negative terms

31. Chapter 16: Cognitive Capabilities - Cognitive Dimensions and the Gulfs (Contd.) • Influences on Decision Making: Learning and Feedback • Let users make decision without feedback • Users get more confident • Give users feedback on decision making • Users get better • Cognitive Dimensions • Hidden Dependencies • How visible relationships are between components • Example: Spreadsheets show formula in one direction • Viscosity • How easy is it to change the system • Example: A word document with figure numbers typed manually • Implications: Designers should make dangerous actions viscous

32. Chapter 16: Cognitive Capabilities - Cognitive Dimensions and the Gulfs (Contd.) • Cognitive Dimensions • Role expressiveness • How clear the mapping of objects are to their functions • Example: Buttons on interface being clearly buttons • Banners or logos as buttons could be misleading • Premature commitment • How soon does the user have to decide something • Example: Some databases require planning record structures and size limits on them before entering any data

33. gulf of execution Physical System Goals Chapter 16: Cognitive Capabilities - Cognitive Dimensions and the Gulfs (Contd.) • What the four stages model reveals • The “Gulf of Execution” • Do actions provided by system correspond to the intentions of the user? • Gulf: Amount of effort exerted to transform intentions into selected and executed actions • A good system: • Direct mappings between Intention and selections • e.g. printing a letter: • put document on printer icon • vs select print from menu

34. Chapter 16: Cognitive Capabilities - Cognitive Dimensions and the Gulfs (Contd.) • What the four stages model reveals • The “Gulf of Evaluation” • Can feedback be interpreted in terms of intentions and expectations? • Gulf: Amount of effort exerted to interpret feedback • A good system: Feedback easily interpreted as task expectations • e.g. graphical simulation of text page being printed • A bad system: No feedback or difficult to interpret feedback • e.g. Unix: “$”, “bus error”, “command not found” gulf of evaluation Physical System Goals

35. Chapter 16: Cognitive Capabilities - Cognitive Dimensions and the Gulfs (Contd.) • Implications of the Gulfs for Design • Make gulfs narrower where appropriate • Allow visibility of appropriate information for achieving relevant tasks • Feedback, consistency, and understanding users mental models can reduce the gulfs • Make gulfs wider where appropriate • Relevant for dangerous and expensive actions • Hide components • Make unavailable action impossible to do • Do not give any feedback

36. Chapter 5: Behavioral: Basic Psychology of the Senses of the User (Contd.) • Sensation • The experience of sensory information • Determined by stimulus quality and sensory organ • Objective process • Perception • The process of creating meaningful patterns from raw sensory information • Influenced by past experiences, expectations, and feelings • Subjective process • Habituation • Habituation occurs when percept occurs repeatedly without importance • Over time stimuli seems less important and perceptible

37. Chapter 5: Behavioral: Basic Psychology of the Senses of the User (Contd.) Types of responses to a signal Signal Detection Theory SDT measures how accurate is performance Gives a way to analyze complex situations

38. Chapter 5: Behavioral: Basic Psychology of the Senses of the User (Contd.) Key parameter: Distinguish signal from noise Signal normally distributed some distance away from 0 Noise is distributed around 0 Threshold (Criterion response) – parameter that the observer adjusts Area of signal distribution correctly classified as signal(to the right of threshold) – Hits Area of signal to left of threshold – Miss Noise classified as signal to the right of threshold – False alarm Noise to the left of threshold - Correct rejection Distance and threshold can be computed from their ratio using tables from normal distribution

39. Chapter 5: Behavioral: Basic Psychology of the Senses of the User (Contd.) • Two stages in vision • Physical reception of stimulus • Processing and interpretation of stimulus • Retina • Center of retina has most of the cones • Allows for high acuity of objects focused at center • Edge of retina is dominated by rods • Allows detecting motion of threats in periphery • Photo-pigments not distributed evenly • Mainly reds (64%) & very few blues (4%) • Center of retina (high acuity) has no blue cones • Disappearance of small blue objects you fixate on

40. Chapter 5: Behavioral: Basic Psychology of the Senses of the User (Contd.) • Different wavelengths of light focus at different distances behind eye’s lens • Need for constant refocusing • Causes fatigue • Be careful about color combinations • e.g., no blues at the same time as reds

41. Chapter 5: Behavioral: Basic Psychology of the Senses of the User (Contd.) • Color Guidelines • Avoid red & green in the periphery - why? • Lack of RG cones there -- yellows & blues work in periphery • Avoid pure blue for text, lines, & small shapes • Blue makes a fine background color • Avoid single-color distinctions • Mixtures of colors should differ in 2 or 3 colors • e.g., 2 colors shouldn’t differ only by amount of red

42. Chapter 11: Errors: An Inherent Part of Human-System Performance (Contd.) • What is error? • Precursors to accidents • Errors trigger a chain of events • Types of errors • Perceptual errors (B8, Z2, I1) • Cognitive errors (Memory, Link, Inconsistent) • Motor errors (Hand, Eye) • Options very close to each other • Slips, errors, erroneous knowlege • How to gather data to study errors? • Laboratory-based experiments • Field-based observations • Archive data • Combination methods are better

43. Chapter 11: Errors: An Inherent Part of Human-System Performance (Contd.) • Analyzing Errors • Event trees • Bottom up technique • Sequence of events leading to all possible outcomes • Based on binary logic (Each node in tree has 2 possible branches; Yes / No) • Each event can be assigned a probability • Sum of probabilities corresponding to each node must be 1 • Probability of different outcomes can be calculated by multiplying (ANDing) together all event probabilities along the path that leads from initiating event to outcome

44. Chapter 11: Errors: An Inherent Part of Human-System Performance (Contd.) • Fault trees • Top down technique • Start with outcome and work backwards to find all causes • Does not need to be binary tree • Outcome can be determined by either ANDing or ORing together a set of possible causal factors • Can be qualitative or quantitative • Quantitative fault tree – Probability of occurrence is allocated to each of lowest level leaf nodes in tree