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Task AnalysisTask Analysis
IACT 403 IACT 931 CSCI 324Human Computer Interface
Lecturer: Gene Awyzio
Room: 3.117Phone: 4221 4090Email: [email protected]
OverviewOverview
What is task analysis?Task Analysis Methods
task decomposition knowledge based analysis entity-relationship techniques
Sources of InformationUses of Task Analysis.
What is Task Analysis?What is Task Analysis?
Methods of analysing people's jobs: what people do what things they work with what they must know
What is Task Analysis?What is Task Analysis?
Example: in order to clean the house
get the vacuum cleaner outfix the appropriate attachmentclean the roomswhen the dust bag gets full, empty itput the vacuum cleaner and tools away
Must know about:vacuum cleaners,their attachments, dust bags,
cupboards, rooms etc..
Approaches to task analysisApproaches to task analysis
Task decomposition splitting task into (ordered) subtasks
Knowledge based techniques what the user knows about the task and
how it is organised
Approaches to task analysisApproaches to task analysis
Entity-relation based analysis relationships between objects and
actions and the people who perform them
General method: observe
unstructured lists of words and actions organise
using notation or diagrams
Differences from other techniquesDifferences from other techniques
Systems analysis focus - system design
Task analysis focus - the user
Differences from other techniquesDifferences from other techniques
Cognitive models focus - internal mental state granularity - practiced `unit' task
Task analysis focus - external actions granularity - whole job However
much overlap in generaldifferences have exceptions
Task DecompositionTask Decomposition
Aims: describe the actions people do structure them within task subtask hierarchy describe order of subtasks
Focus on Hierarchical Task Analysis (HTA) It uses:
text and diagrams to show hierarchyplans to describe order.
Textual HTA descriptionTextual HTA description
Hierarchy description … 0. in order to clean the house
1. get the vacuum cleaner out2. fix the appropriate attachment3. clean the rooms
• 3.1. clean the hall• 3.2. clean the living rooms• 3.3. clean the bedrooms
4. empty the dust bag5. put vacuum cleaner and attachments away
Textual HTA descriptionTextual HTA description
... and plans Plan 0:
do 1 - 2 - 3 - 5 in that order.when the dust bag gets full do 4
Plan 3: do any of 3.1, 3.2 or 3.3 in any order depending on which rooms need cleaning
N.B. only the plans denote order.
Generating the hierarchyGenerating the hierarchy
get flat list of tasksgroup tasks into higher level tasksdecompose lowest level tasks furtherStopping rules How do we know when to
stop? Is “empty the dust bag" simple enough?
Purpose: expand only relevant tasksError cost: stop when P x C is smallMotor actions: lowest sensible level.
line under box means no further expansion.
Plans shown on diagram or written elsewhere.
Same information as: 0. make a cup of tea
1. boil water...
Diagrammatic HTADiagrammatic HTA
Refining the descriptionRefining the description
Given initial HTA (textual or diagram) How to check/improve it? Some heuristics:
paired actions• e.g., where is `turn on gas’
restructure• e.g., generate task `make pot’
balance• e.g., is `pour tea' simpler than making pot?
Generalise• e.g., make one cup or two... or more.
Types of planTypes of plan
fixed sequence e.g., 1.1 - 1.2 -1.3
optional tasks e.g., if the pot is full 2
waiting for events e.g., when kettle boils 1.4
cycles plan 5 5.2 empty cups? for each guest 5.3
No
Yes
5.1
Types of planTypes of plan
time-sharinge.g., do 1; at the same time …
discretionarye.g., do any of 3.1, 3.2 or 3.3 in any order
mixturesmost plans involve several of the above.
Knowledge Based AnalysesKnowledge Based Analyses
Focus on: Objects - used in task Actions - performed Taxonomies represent levels of abstraction
Knowledge Based AnalysesKnowledge Based Analyses Example:
motor controls steering steering wheel,
indicators engine/speed
direct • ignition, accelerator,
foot brake gearing
• clutch, gear stick lights
external • headlights, hazard
lights internal
• courtesy light
wash/wipe wipers
• front wipers, rear wipers
washers • front washers, rear
washers heating
• temperature control, air direction, fan, rear screen heater
parking • hand brake, door lock
radio numerous others
TDH notationTDH notation
TDH - Task Description HierarchyThree types of branch point in taxonomy:
XORnormal taxonomyobject in one and only one branch
AND object must be in bothrepresents multiple classifications
OR weakest casecan be in one, many or none
TDH notationTDH notation
Example: wash/wipe AND
function XOR• wipe
– front wipers, rear wipers• wash
– front washers, rear washersposition XOR
• front– front wipers, front washers
• rear– rear wipers, rear washers.
Larger TDH exampleLarger TDH example kitchen item AND
shape XORdished
• mixing bowl, casserole, saucepan, soup bowl, glassflat
• plate, chopping board, frying pan function OR
preparation• mixing bowl, plate, chopping board
cooking• frying pan, casserole, saucepan
dining XOR• for food
– plate, soup bowl, casserole• for drink
– glass
More on TDHMore on TDH
Uniqueness rule: can the diagram distinguish all objects?
e.g., plate is:• kitchen item/shape( flat)/
function{preparation,dining(for food)}/• nothing else fits this description
More on TDHMore on TDH
Actions have taxonomy too: kitchen job OR
preparation• beating, mixing
cooking• frying, boiling, baking
dining• pouring, eating, drinking.
Abstraction and cutsAbstraction and cuts
After producing detailed taxonomy `cut' it to yield abstract view.
That is, ignore lower level nodes. e.g., cutting above shape and below
dining, plate becomes:kitchen item/function
{preparation,dining}/
Abstraction and cutsAbstraction and cuts
This is a term in Knowledge Representation Grammar
(KRG)These can be more complex:
`beating in a mixing bowl' becomeskitchen job(preparation)
•using a kitchen item/ function {preparation}/.
Entity-Relationship Based TechniquesEntity-Relationship Based Techniques
Emphasis on objects, actions and their relationships Similar to object-oriented analysis, but …
includes non-computer entitiesemphasises domain understanding not
implementation
Entity-Relationship Based TechniquesEntity-Relationship Based Techniques
Running example: `Vera's Veggies' - a market gardening firm
Owner/manager: Vera BradshawEmployees: Sam Gummage and Tony Peagreenvarious tools including a tractor `Fergie’two fields and a glasshousenew computer controlled irrigation system.
ObjectsObjects
Start with list of objects and classify them:Concrete objects:
simple things: spade, plough, glasshouseActors:
human actors: Vera, Sam, Tony, the customers what about the irrigation controller?
ObjectsObjects
Composite objects: sets: the team = { Vera, Sam, Tony } tuples: tractor may be < Fergie, plough >
To the objects add attributes: Object Pump3 simple - irrigation pump
Attributes:• status: on/off/faulty• capacity: 100 litres/minute
N.B. need not be computationally complete
ActionsActions
List actions and associate with each: agent - who performs the actions patient - which is changed by the action instrument - used to perform action
Examples: Sam (agent) planted (action) the leeks (patient) Tony dug the field with the spade (instrument)
ActionsActions
Note: implicit agents - read behind the words
`the field was ploughed' - by whom? indirect agency - the real agent?
`Vera programmed the controller to irrigate the field’ messages - a special sort of action
`Vera told Sam to …’ rôles - an agent acts in several rôles
Vera as worker or as manager.
E/R Example I - objects and actionsE/R Example I - objects and actions
Object Sam human actor Actions:
S1: drive tractor S2: dig the carrots
Object Vera human actor - the proprietor Actions: as worker
V1: plant marrow seed V2: program irrigation controller
Actions: as manager V3: tell Sam to dig the carrots
Object the men composite Comprises: {Sam, Tony}
E/R Example I - objects and actionsE/R Example I - objects and actions
Object glasshouse simple Attribute:
humidity: 0-100%
Object Irrigation Controller non-human actor Actions:
IC1: turn on Pump1IC2: turn on Pump2IC3: turn on Pump3
Object Marrow simple Actions:
M1: germinateM2: grow.
EventsEvents
Events are when something happens performance of action
`Sam dug the carrots’ spontaneous events
`the marrow seed germinated’`the humidity drops below 25%’
timed events`at midnight the controller ...'
RelationshipsRelationships
object - object social - Sam is subordinate to Vera spatial - pump 3 is in the glasshouse
action - object agent - (listed with object) patient and instrument
RelationshipsRelationships
actions and events temporal and causal
`Sam digs the carrots because Vera told him’
Temporal relations also use HTA or dialogue notations. show task sequence (normal HTA) show object lifecycle (see page 241).
E/R example II - events and relationsE/R example II - events and relations
Events Ev1: humidity drops below 25% Ev2: midnight
Relations: object - object location ( Pump3, glasshouse ) location ( Pump1, Parker's Patch )
E/R example II - events and relationsE/R example II - events and relations
Relations: action - object patient ( V3, Sam )
Vera tells Sam to dig patient ( S2, the carrots )
Sam digs the carrots … instrument ( S2, spade )
… with the spade
E/R example II - events and relationsE/R example II - events and relations
Relations: action - event before ( V1, M1 )
the marrow must be sown before it can germinate triggers ( Ev1, IC3 )
when humidity drops below 25%, the controller turns on pump 3
causes ( V2, IC1 ) the controller turns on the pump because Vera
programmed it.
Sources of InformationSources of Information
Documentation N.B. manuals say what is supposed to happen but, good for key words and prompting
interviewsObservation
formal/informal, laboratory/field (see Chapter 11)
Interviews the expert: manager or worker? (ask both!).
Early analysisEarly analysis
Extraction from transcripts list nouns (objects) and verbs(actions) beware technical language and context
`the rain poured’`I poured the tea’
Sorting and classifying grouping or arranging words on cards ranking objects/actions for task relevance (see
Ch. 11) use commercial outliner
Early analysisEarly analysis
Iterative process: data sources analysis
But costly, so use cheap sources where available.
Uses of Task Analysis IUses of Task Analysis I Manuals and
Documentation Procedural `how to do it'
manual from HTA description useful for extreme
novices or when domain too
difficult assumes all tasks
known
To make cups of tea
boil water - see page 2empty potmake pot - see page 3wait 4 or 5 minutespour tea - see page 4
-page 1-
Make pot of teaonce water has boiledwarm potput tea leaves in potpour in boiling water
-page 3-
Conceptual manualfrom knowledge or
entity/relation based analyses
good for open ended tasks
Example: tea making manual from HTA
Uses of Task Analysis IIUses of Task Analysis II
Requirements capture and systems design lifts focus from system to use suggests candidates for automation uncovers user's conceptual model
Uses of Task Analysis IIUses of Task Analysis II
Detailed interface design taxonomies suggest menu layout object/action lists suggest interface objects task frequency guides default choices existing task sequences guide dialogue design
NOTE. task analysis is never complete rigid task based design inflexible system
QuestionnairesQuestionnaires
Set of fixed questions given to users.Advantages:
quick and reaches large user group can be analysed more rigorously
Disadvantages less Flexible less probing
Need careful design what information is required? how are answers to be analysed?
Question TypesQuestion Types
Dichotomous Multiple Choice Multiple Response Open Ended Rank/Match Likert Semantic Differential Rating
Dichotomous Dichotomous
These are designed to be answered yes or no. The respondent should have the opportunity to answer "I don't know" or "I don't remember".
e.g. Do you use sampling in your production process? Yes
No
I don't know
Dichotomous Dichotomous
Advantages of dichotomous questions: easy to ask easy to understand quick to ask quick/easy to record easy to analyse
Disadvantage misunderstandings are possible as shades of
meaning are not incorporated to derive detailed information, a large number of such questions would need to be asked
Multiple Choice Multiple Choice
Multiple-choice questions permit only one answer. By convention, radio-buttons are used on computer screens where only one option is allowed. Respondent should also be able to answer "I don't know".
e.g. How would you rate the programme? Very PoorPoorFair
GoodVery Good
Multiple Choice Multiple Choice
Advantages of multiple-choice questions: allow many shades of meaning in answers give respondent freedom of choice easily recorded easy to analyse
Disadvantages difficult to ensure list of answers is complete difficult to phrase initially exclusive answers the list of answers should not be too long
Multiple Response Multiple Response
Multiple-response questions can have two or more answers.
By convention, check-boxes are used on computer screens where several options are allowed.
Respondent should also be able to answer "I don't know", "all" or "none".
Questions can have any number of responses or a fixed number as illustrated below. e.g. Which three of the
following best describe the show? Fun
nyInteresting
Educational
Diverting
Boring
Offensive
Multiple Response Multiple Response
Advantages of multiple-response questions allow many shades of meaning in answers give respondent freedom of choice easily recorded easy to analyse
Disadvantages difficult to ensure list of answers is complete difficult to phrase initially exclusive answers the list of answers should not be too long
Open Ended Open Ended
Designedto give respondent complete freedom of choice in answering and thus derive maximum information.
Often used where there is insufficient information available on a topic to permit complete lists of alternative answers.
Difficult to analyse with computers. e.g. How enjoyable did you find the presentation?
Open Ended Open Ended
Some structure can be added using the following techniques:
Word association Words are presented, and respondents note the first
word that comes to mind. e.g. What is the first word that comes to your mind
when you see the following? Your mother
Open Ended Open Ended
Sentence completion Incomplete sentences are presented, and respondents
complete them. e.g. When I choose a beer, the most important
consideration in my decision is
Open Ended Open Ended Advantages of open-ended questions
produce extensive information responses are free from bias of suggested answers many facets of respondent's behaviour revealed
Disadvantages can require slow verbatim recording interviewers tend to select information they believe significant lengthy interviews difficult to analyse many incoherent answers much irrelevant information received analysis requires groupings of answers - which loses much of the
shades of meanings
Rank/Match Rank/Match
e.g. Rank the following factors in order of importance when you buy a car
After sales support
Brand name
Value for money
Fuel economy
Appearance
Other (please specify)
Likert Likert
Likert questions are statements with which the respondent indicates the amount of agreement/ disagreement. e.g. Small shops generally give better service than
large onesStrongly agreeAgree
Neither
DisagreeStrongly disagree
Semantic Differential Semantic Differential
In this type of question a scale is inscribed between two bipolar words, and the respondent selects the point that represents the direction and intensity of his or her feelings.
e.g. How would you describe your views on shops opening on Sundays? Modern Old-fashioned
Question SequenceQuestion SequenceThere are a number of general rules which
should be considered when the order of the questions is arranged.
Those questions which are easy to answer should be put at the beginning, in order to give the respondent confidence in his ability to help you.
Those questions which are likely to interest the respondent should be early in the order.
The questions should be asked in a logical order.
Question SequenceQuestion SequenceFilter questions should follow each other
without being interrupted by other questions.Before a change of topic, introductory
phrases should be used to enable the respondent to make an easy transition.
Personal or emotional questions should be at the end.
More complicated questions should be at the end.
These guidelines tend to imply recommendation of a funnel design: