1. Chapter 5
Task analysis

2. By the end of this chapter you should be able to...
Describe HTA and its features
Explain the purpose of task analysis and modelling
Distinguish between different types of task analysis
Carry out an HTA on an existing system
Explain and show how the results of an HTA can be used to improve the usability of a proposed interactive system

3. 5.2 Task analysis Result Aim Focus
Description of tasks that users do when they interact with a system
Aim
Find out what the old system enables users to do
Focus
Goals and actions (procedures and methods) that users carry out
What users know about their work and tasks
Psychological processes such as perception and memory
Objects and entities on which users act
Relationship between objects and attributes
TA should inform, not constrain development of new system
TA very useful for “walk-up-and-use” systems
Don’t want to train users
System should be as natural as possible

4. 5.3 What is task analysis?
Means of analysing and describing the jobs people do
Provides both method and notation
Focus on
peoples’ goals and the actions they carry out
things people know (skills and abilities)
the things they act on

5. 5.4 Purposes of task analysis
Help designers to understand existing systems, tasks and skills required in people’s existing jobs.
Advantage
Contributes to better understanding of users’ requirements
Evaluation of existing system
Assists in design of new system
Triggers insights of how to do the task better
Notation
Simple and descriptive
Should cover both tasks and the users

6. 5.5 Approaches to TA Not all tasks structures are hierarchical
HTA not always applicable
Several approaches
HTA
Procedural
Knowledge-based (KB)
Entity-relationship (ER)
Procedural TA
All activities are executed step-by-step, linear and sequential
Directional flow with a start and end
Preceding task must be completed before commencing with next one
Represented in flowchart diagram

7. 5.5.1 Inputs to and outputs of TA
Problem statement
Observation of existing systems
Analysis of users
Outputs
HTA or other document, e.g. matrix
Observations of existing system
Good and bad points
Analysis and profile of the user population
Issues
Who are the users?
How diverse is the user population?
How to provide universal access?
Why don’t people use the system?
Observe goals as well as tasks

8. 5.5.2 Data collection Ask people Observe users working
Assume that they have adequate insight
May not always tell the truth
Observe users working
Users might be nervous, not acting naturally
Users might be conscious not to make mistakes
Users might show only subset of tasks that they know well
Talk to users informally, in focus groups or interviews
Read available documentation or training material
Do the task yourself
Familiarise yourself with existing systems
Analyse real tasks, i.e. don’t set up tasks superficially
Develop abstractions of real tasks
Conduct experiments
Ethnographic methods, social probes, surveys
Contextual enquiries

9. 5.6 Hierarchical Task Analysis
One of the most common forms of TA
Involves
Identifying goals that user wants to achieve
Decomposing goals into tasks
Further decomposing into subtasks
Repeat; stop at the level of actions

10. 5.6.1 HTA example 1: Withdraw cash from ATM
1 Check machine will work
1.1 Look at status indicator
1.2 Look for card logo
2 Insert card
Enter PIN number
Select Language
Initiate withdrawal transaction
5.1 Select withdraw cash
5.2 Specify account
5.3 Enter amount
Complete transaction
6.1 Take card
6.2 Take cash
6.3 Take statement

11. 5.6.2 Adding plans
Hierarchical diagram / text specifies which subtasks are part of a task
Does not specify how the subtasks are carried out
Plans are used to describe
how sub-tasks are combined
order of subtasks
conditional or optional subtasks
optimum way of using sub-tasks
any repetition required or involved
HTA not complete without complete set of plans to guide implementation of sub-tasks
ATM example
Next slide

12. 5.6.2 HTA example: Plans added
0 Withdraw cash
Check machine will work
1.1 Look at status indicator
1.2 Look for card logo
Insert card
Enter PIN number
Select Language
Initiate withdrawal transaction
5.1 Select withdraw cash
5.2 Specify account
5.3 Enter amount
6 Complete transaction
6.1 Take card
6.2 Take cash
6.3 Take statement
Plan 0: do 1;
if possible do 2;
repeat 3 until PIN correctly entered;
do 4;
do 5;
do 6.
Plan 1: do 1.1, 1.2 in any order
Plan 5: do 5.1;
do 5.2;
do 5.3.
Plan 6: wait until card available;
do 6.1;
wait until cash available;
do 6.2;
wait until statement available;
do 6.3.

13. E2: Example 2
The manual task of filing documents in a filing cabinet...
You have an unsorted stack of documents
Your filing cabinet contains folders that are ordered somehow
How do you get all the documents into the correct folder?

14. E2/T0: Filing cabinet 0. Store documents in filing cabinet
1. File lots of documents
2. File one or two documents
Plan 0: Do 1 or 2

15. E2/T2: Filing one or two things
Simply find the appropriate folder and put the documents in...
2. File one or two documents
2.1. Open cabinet
2.2. File each document
2.3. Close cabinet
Plan 2: Do 2.1., (2.2. repeatedly) then 2.3.

16. E2/T2.2: Filing each document
2.2. File each document
Find appropriate file
Open file
Place document in file
Close file
Plan 2.2: Do 2.2.1, , , then

17. E2/T1: Filing lots of documents
Strategy
Sort the documents into order first
then split the sorted documents up into ‘categories’
(ie all the documents whose author begins with ‘A’)
then work through the filing cabinet, putting each category into the right file
1. File lots of documents
1.1. Choose criteria on which documents are sorted
1.2. Sort all documents to be filed into order
1.3. Split documents up into categories
1.4. Open cabinet
1.5. Place each category of document into file
1.6. Close cabinet
Plan 1: Do 1.1., 1.2., 1.3., 1.4., (1.5. repeatedly) then 1.6.

18. E2/T1.1: Choosing sorting criteria
1.1. Choose criteria on which documents are sorted
Choose alphabetical by title of document
Choose alphabetical by author of document
Choose date order
Plan 1.1: Do any one of , , or

19. E2/T1.5: Placing categories in files
1.5. Place each category of document into file
Open file
Place each document in file
Close file
Plan 1.5: Do , ( repeatedly) then

20. 0. Store documents in filing cabinet
HTA: E2
0. Store documents in filing cabinet
1. File lots of documents
1.1. Choose criteria on which documents are sorted
1.2. Sort all documents to be filed into order
1.3. Split documents up into categories
1.4. Open cabinet
1.5. Place each category of document into file
1.6. Close cabinet
2. File one or two documents
Open cabinet
File each document
2.2.1.Find appropriate file
2.2.2.Open file
2.2.3.Place document in file
2.2.4.Close file
Close cabinet
Plan 0: Do 1 or 2
Plan 1: Do 1.1., 1.2., 1.3., 1.4., (1.5. repeatedly) then 1.6.
Plan 2: Do 2.1., (2.2. repeatedly) then 2.3.
Plan 2.2: Do 2.2.1, , , then

21. E2: Things to note... Note … Think about …
The overall task is numbered 0
The tasks are all described by verbs
Each task that is decomposed must have a plan to go with it
Plan X must only refer to sub-tasks to X
Think about …
Imagine that you are designing an electronic filing system
What does this HTA tell you about filing systems?
Which bits of the manual task would you keep, and which would you do away with or redesign?
Why?

22. E3. Example
Jill creates a stack of new catalogues in a corner of her kitchen. When she is preparing dinner, she can flip through a catalogue to see what’s new or on sale or what strikes her interest. In the evening she may pick out five or six catalogues to look at while the family is watching TV. She may even take a few to bed, or to the bath.
Generally she simply browses through pictures, reading descriptions only when the pictures look interesting. When she finds something interesting she may dog-ear the page, draw a circle round it or mark the page with a sticky note. She keeps catalogues with marked pictures around until she wants to make a purchase.

23. Plan 0: do 1 then 2 if item found
E3/T0: Example
0. Using catalogues
1. Browse items
2. Mark items
Plan 0: do 1 then 2 if item found

24. E3/T1: Example Plan 1: do 1.1 or 1.2 or 1.3 or 1.4 0. Using catalogues
1. Browse items
1.1. Browse by what’s new
1.2. Browse by sales
1.3. Browse by items that interest
1.4. Browse by catalogues
Browse in kitchen
Browse while watching TV
Browse in bed
1.4.4 Browse in bath
2. Mark items
Plan 1: do 1.1 or 1.2 or 1.3 or 1.4

25. E3/T2: Example 0. Using catalogues 1. Browse items 2. Mark items
2.1. Circle item
2.2. Mark page
Dog-ear page
Sticky on page
Plan 2: do 2.1 or 2.2

26. E3/T2: Example 0. Using catalogues 1. Browse items 2. Mark items
2.1. Circle item
2.2. Mark page
Dog-ear page
Sticky on page
Plan 2.2: do or 2.2.2

27. 5.6.5 Key features interactive system based on HTA
Flexibility
Interactivity
Portability (Location and hardware)
Flexible browsing capability
Suitable functionality
These are passed as requirements to the design cycle
Not for exam or test purposes: pp68-69

28. Summary
Task analysis gives designers a means of describing how people do their jobs
Serves different purposes in design and development