“the most crucial property of any interactive system is its support for human activity. this is...
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“The most crucial property of any interactive systemis its support for human activity. this is what makesit worth having. it may enable us to do things faster,with fewer errors, with less prior learning, with greater resultant quality, or perhaps just with greaterfun and satisfaction.” [p.6]
Newman, W.M. and Lamming, M.G., 1995, Interactive System Design, Harlow: Addison-Wesley
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“This interdisciplinary degree is concerned with designing interactive technology for people. You will gain skills in software design and systems engineering as well as an understanding of human-computer interaction and computer-mediated communication.”
Course details from University Prospectus
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Layers of Interactive Systems
Socio-technical interaction
Human/computer Interaction
Application Programming
Cognition & Perception
System Programming/Assembly Language
Operating Systems/communications
Machine Language
Sensorimotor
Microprogramming
Physical/Digital LogicFeedback
Physical Inputs
Information & knowledge
Activity & CultureConvention
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Selection in the World
Baber et al., 2000, Interact’00
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Assignment
You will work in small teams to develop a concept design for an interactive museum guide.
You will need to consider: Sensor technologies Display technologies User interface Usability
Your team will present your concept designs in a poster session (10%) in week 8 The layout and contents of the posters will be discussed in a later session
You will produce individual reports on the design (90%) and submit it in week 10 The marking scheme will be given to you on week two
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Usability & Designing for Error1H1
Chris Baber
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Useful Resources
Ergonomics Information Analysis CentreThird Floor (N309)Several hundred books, journals, conference
proceedings on all aspects of interactive systemsErgonomics Abstracts database
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Objectives
Consider why people make mistakes in their interactions with technology
Examine simple approaches to predicting how people use technology
Evaluate the usability of products against ISO9241
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Course Structure
Human Centred Design
Human Error
Predictive Evaluation Methods
Introduction to Usability Evaluation
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Outline syllabus
1. Making sense of technology;
2. Introduce concept of Human Error;
3. Introduce concept of Usability;
4. Review ISO9241 (part 13)
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Reading List
Norman, D.A., 1990, The Design of Everyday Things, New York: Basic Books [The psychology of everyday things]
Noyes, J. and Baber, C., 1999, User-Centred Design of Systems, Berlin: Springer-Verlag
Stanton, N.A., 1998, Human Factors in Consumer Products, London: Taylor and Francis
Nielsen, J., 1993, Usability Engineering,
Boston: Academic Press
http://www.baddesigns.com/index.shtml
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The “Waterfall” Model ofthe Design ProcessRequirements
Design
Implementation
Verification
Maintenance
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Human-Centred Design Process
ISO 134071.Plan human-centred design process
2. Specify context of use
4. Produce design solutions
3. Specify user and organsiationalrequirements
5. Evaluate designagainst requirements
complete
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Making Sense of Technology
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‘Instant Experts’
You get a new mobile telephone for Xmas, do you:
1. Read the manual from cover to cover and then switch on the phone?
2. Switch on the phone and try to use it?
3. Switch on the phone and read the manual when you have problems?
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Using tools
Physical appearance
Knowledge of use
Sequence of activity
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Affordance
See handle Reach out hand Grasp handle Turn handle Pull door
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The Cooker Problem #1
Which control acts on which ring?
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The Cooker Problem #2
Which control acts on which ring?
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Direction of motion Stereotypes
a d
b
c
? ?
Clockwise = increaseClockwise = rightClockwise = away from controlClockwise = increase on scale
1 2 3 4 5 6 7
1 2 3 4 5 6 7
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Clockwise to Increase?
1234567
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Conclusions…
We have learned ‘routines’ for how to use many sorts of technology
We apply these routines ‘automatically’ When the routines succeed, they are
reinforced When the routines fail, we think about what
we’re doing
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Problem Products
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Rule I: to set time turn control;Rule II: to set time < 15s, turn control past 15s and then turn back to desired time
http://www.baddesigns.com/timer.html
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Conflicting labels?
V for volume?
V for
http://www.baddesigns.com/remote.html
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Spatial Compatibility?
http://www.baddesigns.com/boombox.html
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Which side is the handle to open the ‘fridge?
http://www.baddesigns.com/fridge.html
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Make the freezer warmer without changing fresh food setting
Norman, D.A., 1990, The Design of Everyday Things, New York: Basic Books
Normal settings C AND 5Colder fresh food C AND 6-7 1 Set both controlsColdest fresh food B AND 8-9 2 Allow 24 hours toWarmest fresh food D AND 7-8 stabilizeOff (fresh fd & frz) C AND 4-1
A B C D Efreezer
7 6 5 4 3 2 1fresh food
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Possible Explanatory Models:
1. Thermostat and control for each compartment, hence two sets of controls(but why do the controls interact?)
2. Only one thermostat and distribution of cold air varied between compartments (but in which compartment is the thermostat?)
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Using technology
Goals x Appearance (‘System image’)
Expectations x Design
Tasks x Functions
Context x Use
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Norman’s 7 Stages of Action
Norman, D.A., 1990, The Design of Everyday Things, New York: Basic Books
Goal
Intention Evaluation
Plan of action Interpretation
Action Perception
Things in the World
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Task Models
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Hierarchical Task Analysis
Activity assumed to consist of TASKS performed in pursuit of GOALS
Goals can be broken into SUBGOALS, which can be broken into tasks
Hierarchy (Tree) description
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Hierarchical Task Description
1 .0S w itch on O H P
2 .0C h eck p ro jec tion
3 .0P lace fo il on O H P
4 .0F ocu s p ro jec tion
0 .0P resen t O H P s lid es
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Task Analysis comes from adding plans PLANS = conditions for combining tasks Fixed Sequence
P0: 1 > 2 > exit Contingent Fixed Sequence
P1: 1 > when state X achieved > 2 > exit P1.1: 1.1 > 1.2 > wait for X time > 1.3 > exit
Decision P2: 1 > 2 > If condition X then 3, elseif condition Y then 4 >
5 > exit
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Reporting
HTA can be constructed using Post-it notes on a large space (this makes it easy to edit and also encourages participation)
HTA can be difficult to present in a succinct printed form (it might be useful to take a photograph of the Post-it notes)
Typically a Tabular format is used:Task number Task Plan Comments
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Varieties of Task Model
Context People Goals Actions / Tasks
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Diagrammatic Model
Design Team
Methodologyfollows
Experience
Design Rationale
draws upon
represents
Stakeholders
Design briefinforms
defines
consults
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Errors in ATM use
Incorrect PIN Forget PIN Insufficient funds Exceed withdrawal limit Card insertion Following prompts
Slip / Memory Memory Decision / Memory Decision / Memory
Slip Slip / Misinterpretation
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Human Error
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Human Error
Failure of person or failure of design?
Lack of intelligence or lack of information?
Lack of ability or lack of guidance?
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Types of human error
Humanactivity
Unintendedactions
Intendedactions
Slip
Lapse
Mistake
Failure of attentionIntrusionOmissionReversal
Misorder / Mistime step
Failure of memoryOmit stepLose place
Forget intentionWrong procedure
Rule breaking ViolationSabotage
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Skill-based Failure
Double capture: habit intrusion preventing intended deviation from routine
Omission after interruption: lack of attentional check
Reduced intentionality: delay between intention and action
Perceptual confusion: confuse objects
Interference: two current plans converge
Repetition: begin action, interruption, repeat action
Reversal: begin action, interruption and undo action
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Rule-based Failure
First exception: routine action with attentional failure
Countersigns: ignore evidence that rule should not be applied,
Increased Workload: narrowing of attention;
Rule strength: stimuli evoke rule with most strength
Generalisation: frequency bias;
Redundancy: chunking of stimuli;
Rigidity: functional fixedness;
Deficiency: ignore parts of problem space
Wrong rule: misinterpret situation and apply wrong rule
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GEMS
Check action OK? GOAL
Yes
Problem? No Problemsolved?
Availableinformation
Familiar Yes Apply knownpattern? rule
No
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GEMS (continued)
Find analogy Apply known rule
None found
Develop mental model Infer diagnosisOf problem space. Apply rules YesDefine abstract relations
NoProblem solved?
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Human Error Prediction
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Failure Mode Effect Consequence Analysis Human Activity can fail in predictable ways
E.g., Task: Type PIN Failure Modes: recall wrong PIN, type PIN incorrectly,
don’t type anything, use wrong keypad…
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SHERPA Action
1. Omitted2. Too early3. Too late4. Too much5. Too little6. Too short7. In wrong direction8. Right action on wrong object9. Wrong action on right object
Information1. Not obtained2. Wrong information
obtained Communication
1. No communication2. Wrong information
Check1. Omitted2. Wrong object3. Wrong check4. mistimed
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Tabular Format
HTA
Task Failure Mode Effect Consequence
1.1 Insert card Action: 7/8/9 Card not inserted
No access; Repeat task
1.2 Check prompt Check: 1 Fail to read screen
Do not check ATM status
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TAFEI
Task Analysis for Error Identification
State-transition model of human interaction with products
Consider possible transitions for each state
Ask whether transitions are ‘legal’, (needed to fulfil specific goal)
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Flowchart for TAFEI
Define components / materials
Define user goals / tasks Define device states / transitionsfor specific user goal
Relate user tasks to state transitions
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Analysing TAFEIDraw transition matrix
For cell i,j, ask:is it possible to move to ALL other states
IF YES and related to goal, Then LEGAL
IF YES and not related to goal,Then ILLEGAL
IF NO,Then IMPOSSIBLE
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TAFEI state
00
Mini-disc Off; headphones out
Waiting for:On
Headphones inOpen cover
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TAFEI state
00
Mini-disc Off; headphones out
Waiting for:On
Headphones inOpen cover
11
Mini-disc Off; headphones in
Waiting for:On
Headphones inOpen cover
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TAFEI state
00
Mini-disc Off
Waiting for:On
Headphones inOpen cover
11
Headphones in
Waiting for:On
Headphones outOpen cover
2
22
Mini-disc On
Waiting for:Off
Headphones outOpen cover
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LUL Ticket Machine
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Transition Matrix
From State:
To State:
012345
0 1 2 3 4 5
II----
LII---
IILI--
IIILL-
IIIIIL
IIIILL
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Redesigning User Interface Using TAFEI: two examples
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Microscope Control: Original Design
Menu driven Menus accessed by first
letter of command Menus arranged in
hierarchy
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TAFEI of original design
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Problems with original design
Lack of consistency D = DOS commands; Delete; Data file; Date
Hidden hierarchy Only ‘experts’ could use
Inappropriate defaults Setting up a scan required ‘correction’ of default settings
three or four times
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Initial design activity
Observation of non-technology work Cytogeneticists inspecting chromosomes
Developed model of task Hierarchical task analysis
Developed design principles, e.g., Cytogeneticists as ‘picture people’ Task flow Task mapping
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Task Model
Work flows between specific activities
Patient details Administration
Set up
Reporting
Microscope
Cell sample
Analysis
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First “prototype”
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TAFEI of first prototype
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Second prototype
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Final Product
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Conclusions
Graphical user interface based on task activity Recognition not recall Task flow based on work Terminology from work not computer Accessible to non-technical
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Gas Analyzer
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Results of Redesign
Figure 9: Total wrong key presses and error screens encountered using the original and re-designed LMS
interface
0
10
20
30
40
50
Original Re-design
LMS version
key
pre
sse
s
wrong key presses
error screen encountered
Figure 12: Time taken to complete the task for the original and re-designed versions of the LMS.
0
0.5
1
1.5
2
2.5
original re-design
LMS version
Tim
e i
n m
inu
tes
time
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Usability
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Interactive System Design
Build prototype
Analyse
Modifications
Enhance
Study Users
Specify
EvaluateActivity data
Prototype
Specify
Activitymodel
Usability/errorreport
Newman, W.M and Lamming, M., 1985, Interactive Systems Design, Reading, MA: Addison-Wesley
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User-Centred Design of Systems[Noyes and Baber, 1999]
Who will use the system? What will the system be used for? What are the main components of the system? How will the system be designed? How well do the users think the system works? How well does the system really work? How well does the system under development work? Can the system be improved? How can the system be introduced into the workplace? How will the system be used in the workplace?
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Forms of evaluation
Understand use of technology at work
Comparison of products
Comparison with Standards
Comparison with design targets
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Evaluation in Design
Summative – at end of design
Formative – during design, e.g.,Early
Set objectives, define requirements, existing solutions
Mid Compare with objective, settle disputes, prototypes
LateCompare with Standards and competitors
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Evaluation in Design
Performance factors
Organisationalfactors
Desired Performance
Contextfactors
Relevantmethods
Evaluation Protocol
Actualperformance
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Defining usability
“Usability measures: the effectiveness, efficiency and satisfaction with which specified users can achieve goals in a particular environment.” [ISO9241]
Usability measuresSpecified User
GoalsParticular Environment
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Evaluation Process
user
task
equipment
environment
product
Context of use
goalsIntended objectives
Outcome of interaction
effectiveness
efficiency
attitude
Usability measures
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Specified Users
Skills & Knowledge
Product experience
System knowledge
Task experience
Organisational experience
Training
Operating skills
Qualifications
Linguistic ability
Physical attributes
Vision
Hearing
Manual dexterity
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Goals & Tasks
Definition of typical tasks in typical work domain
Selection of typical goals for typical users
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Particular Environment
Typical domain:OrganisationProductSystemTaskOperating skills
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Evaluation Methods
Analytic methods Specialist reports
User reports Observational methods
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Specialist reports
Evaluation by Experts
Expertise in:ProductDomainTask
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Metrics for Specialist report
HEURISTIC EVALUATION
Simple, natural language User’s languageMinimal memory load ConsistencyUseful feedback Clear exitsClear shortcuts Useful error messagesMinimise user error
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Detecting Problems
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Designing for Error
Change the design of productModes Interlocks
Change the operation of the productTask flowConsistencyClarity / GuessabilitySimplicity
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Designing for Usability
Learnable Efficient
Acceptable Flexible
Useful Enjoyable Elegant