extended cognitive walkthrough judy kay chai: computer human adapted interaction research group...
TRANSCRIPT
Extended Cognitive Walkthrough
Judy Kay
CHAI: Computer human adapted interaction research group
School of Information Technologies
2
Overview
• Predictive method • (with caveat Grigoreanu et al)
• Cognitive Walkthrough
• Benefits
• Disadvantages
(About 50,000 results from Google)
3
Postconditions for this class
• Describe the uses of Cognitive Walkthrough• Describe the processes for conducting Cognitive
Walkthrough analyses• Describe advantages and limitations
• Ability to perform a Cognitive Walkthrough study • Justify the use of Cognitive Walkthrough in the
overall testing of a pervasive computing application
4
• Focus on learnability• Appropriate for novice or casual users
• cf Think-Aloud?
• Does not focus on speed• cf Think-Aloud?
• Sequence is not known prior to inspection• Assesses user success and recovery from errors• Conducted by experts
• cf Think-Aloud?
5
Model of Exploratory Learning
• User has task– 0. will user understand this sub-task is needed?
• Explores system for useful elements– 1. will correct action be obvious? eg button visible
– 2. will user understand instructions? eg user understands the label on the button
• Selects one to try• User interprets system response
– 3. will user know if progress has been made?
Extended Cognitive Walkthrough
Takes account of mental model…..
7
• User has task– 0. will user understand this sub-task is needed
(given their mental model)
• Explores system for useful elements– 1. will correct action be obvious?
– (given their mental model)
– 2. will user understand instructions?
– (given their mental model)
• Selects one to try• User interprets system response
– 3. will user know if progress has been made?
– (given their mental model)
8
Example with basic CW
• Design a cash-operated machine for quick, easy purchase of train tickets by passengers, without training
• Abstract user goals:• Buy a ticket to the required destination
• Determine whether I can afford to buy the ticket to a particular destination
Adapted from Newman and Lamming,
Interactive System Design, 1995)
9
Example with basic CW
• Design a cash-operated machine for quick, easy purchase of train tickets by passengers, without training
• Designer goal breakdown to subgoals:• Determine fare to pay
– indicate destination
– indicate one-way or return
• Dispense ticket– pay money
– get ticket and change
Adapted from Newman and Lamming,
Interactive System Design, 1995)
10
The interface – lo-fi prototype
Concrete user task
Class activity: define 3 concrete tasks
12
The interface – lo-fi prototype
Concrete user task
Buy a one-way ticket to Town Hall
14
The task:
Buy a one-way ticket to Town Hall
15
How designer wants it to work – method 1 where use does not use keypad• Click destination
• ie Town Hall
• Click journey type• ie one way
16
• 0. Task?– Buy one-way ticket to Town Hall
• 1. Is correct action obvious?– Two possibilities:
• Destination
• One way / return
– Will user know both must
be set?
17
How to Help the User?
• Indicate extra information needed• Indicate steps 1 and 2 can be done in either order• Give some feedback on effect of each select action• Reorganise layout so that Steps 1 and 2 are
followed by the fare display
We alter our lo-fi prototypeand check this
19
• 2. Will user understand instructions?
• 3. Will user interpret machine action correctly?
20
• 2. Will user understand instructions?– Yes – due to labels and instructions
• 3. Will user interpret machine action correctly?– Yes (buttons light up, new state appears)
21
22
• 1. Correct action obvious?– Yes
• 2. Will user understand instructions?– Yes
• 3. Will user interpret machine action correctly?– Yes
23
Paying
• 1. Correct action obvious?
• 2. Will user understand instructions?
• 3. Will user interpret machine action correctly?
What are the cases to consider for payment (in cash)
Consider case where user has exact change
25
Paying
Designer intends user to • Pay in money and click • Click “4. Press for ticket”• User then lifts flap to collect the ticket
26
Paying – exact change case
• 1. Correct action obvious?– Yes
• 2. Will user understand instructions?– Yes
• 3. Will user interpret machine action correctly?– Unclear (no feedback on money accepted so far)
We alter our lo-fi prototypeand check this
28
Revised design gives feedback on amount paid so far
Consider other cases eg user realises they have insufficient money
30
Buying a Ticket: Insufficient Money?
• 1. Correct action obvious?
31
Summary of Flaws (so far)
• Confusion about need for steps 1 and 2• No feedback on amount deposited• No means to get money back• So far …...
32
Goals and Tasks
In this example:
Goal: buy a ticket
Sub-goals: (determine fare) and pay
User tasks: concrete cases used in CW
33
Extended cognitive walkthrough
• Adding user's mental model
• What does user believe?• How do you find this out?• What did we assume about the user’s mental
model?• What differences are there in the MM for:
• A novice user
• An expert user
Class activity:
List aspects of the user’s MM that would be relevant to the train ticket interface
What are the implications of some likely cases:
user familiar with existing interfaceuser familiar with a different bus ticket interface
Class activity on Extended CW:
37
Interface is info3315 website
Task
• INFO3315 student has just started semester and wants to determine the deadline for the first assessed work
• Define the relevant mental model
38
Mental Model
• Class web site is at
http://www.ug.it.usyd.edu.au/~info3315
• There is a lecture and a lab each week for most classes
• There is assessed practical work for most classes
• There are fixed deadlines for such work
39
Task sequence
• Go to class web site is at
http://www.ug.it.usyd.edu.au/~info3315
• [This is the home page]
• See the heading “Labs and Deadlines”
• Scan down to “Deadline: Prototype demos”
• This is listed under 19 Sep, Week 8
40
• User has task– 0. will user understand this sub-task is needed
(given their mental model)
• Explores system for useful elements– 1. will correct action be obvious?
– (given their mental model)
– 2. will user understand instructions?
– (given their mental model)
• Selects one to try• User interprets system response
– 3. will user know if progress has been made?
– (given their mental model)
41
• User has task– 0. will user understand this sub-task is needed – Yes
• Explores system for useful elements– 1. will correct action be obvious? – Perhaps not
– may go to “assessment page” as mental model primes them for the word “Assessment” and that page does not have dates
– may miss the “Deadline” in the heading– 2. will user understand instructions?– Perhaps not
– may well see Sep 19 (lecture date) and think that is the deadline
• Selects one to try• User interprets system response
– 3. will user know if progress has been made? – In this simple task the user does not need to take action
(so we can fit all this on a slide)
42
Potential GOTCHAs
• Need to have a prototype that is complete enough for a walkthough of an interesting concrete case
• But this is a technique for early in design process, where designer is ready to change it
• You then need to define:• the users, and their relevant MMs• a good set of tasks• the correct steps (intended by designer)
• Evaluator must imagine people’s thoughts on first using this interface• Keep referring to the mental model• Carefully assess vocabulary/text in terms of mental model
• Repeat process over the tasks, and for each important class of mental model
43
Returning to the reading…. A very impure CW that call ICW
• Additional forms of CW
• Expert evaluator leads the process
• Works with development team reps
• Agile process
• Some Validation (cf lab trial of SSCW part)
• Two stages:• Earlier is SSCW – “Simplified Streamlined”
• Later involves users in SPW – “Simplified Pluralistic”
44
Summary of uses
• Relatively inexpensive in our very, very lightweight approach
• Desk check– No users
– Better with expert evaluators
• Generally applicable
• Novice, casual, intermittent users
• Focus on learnability
45
Summary of usefulness
• Really useful technique, even for designer
• Better if done by • Outsider
• Expert
• But students and non-expert evaluators still can gain from using it
• Part of early usability evaluation because• Low cost
• No users needed