Midterm Review

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Midterm Review

• IST 331 Design and Organization of Information
  Systems User and System Principles

Instructor Mithu Bhattacharya Small revisions by
Frank Ritter Spring 2011
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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

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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

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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 peoples interaction with
  computer-based applications
• Computer Supported Cooperative Work
• Focus on peoples communication through
  computer-based applications

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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

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Chapter 2 History of Human Centered Design
(Contd.)

• Hawthorne Effect
• Performance improvements due to psychological
  factors
• Not physiological

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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

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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

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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
• Teams tolerance to the 2 factors different
• Tolerance correlates to team maturity level

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

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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

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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

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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 havent 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)

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Chapter 3 User Characteristics Bodies,
Behavior, Thinking, and Groups the ABCS (Contd.)

• Fitts Law
• Time to point to an object related to distance
  from object and inversely related to size of
  object

d
Time 70 ms Log 2 (Target distance / Target
size 0.5) (Card, Moran, and Newell, 1983)
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Chapter 6 Cognitive Capabilities Memory,
Attention, and Learning
The Stages of User Activities When Performing a
Task
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Chapter 6 Cognitive Capabilities Memory,
Attention, and Learning (Contd.)

• The Model Human Processor Developed by Card,
  Moran Newell (1983)

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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

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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

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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

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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

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Chapter 6 Cognitive Capabilities Memory,
Attention, and Learning (Contd.)

• Rasmussens 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

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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

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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

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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

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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

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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

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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 users 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

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Chapter 8 Cognitive Capabilities Mental
Representations and Problem Solving (Contd.)

• Simple Decision Making
• Hick-Hyman law
• Tab log2(n1)
• Ttime to make a decision, nnumber 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?

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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

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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

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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

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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

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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
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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

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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

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Chapter 5 Behavioral Basic Psychology of the
Senses of the User (Contd.)

• Signal Detection Theory
• SDT measures how accurate is performance
• Gives a way to analyze complex situations

Types of responses to a signal
Signal Present Signal Present
Response Yes No
Yes Hit False Alarm
No Miss Correct Rejection
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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

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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

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Chapter 5 Behavioral Basic Psychology of the
Senses of the User (Contd.)

• Different wavelengths of light focus at different
  distances behind eyes lens
• Need for constant refocusing
• Causes fatigue
• Be careful about color combinations
• e.g., no blues at the same time as reds

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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 shouldnt differ only by amount of
  red

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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

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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

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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