1. Understanding Task Analysis
NIK ISROZAIDI NIK ISMAIL

2. Learning outcomes At the end of this lecture, you should be able to:
Draft the Hierarchical Task Analysis (chart or textual based)

3. Key terms
Task analysis
Hierarchical task analysis

4. Task Analysis - What’s a Task?
A set of human actions that contributes to a functional objective and to the goal of the system.
Scope or size of a task is determined by the definition of the objectives.
Each task should be approximately equal in size.
But not always the case

5. Task - Decomposition

6. Task - Decomposition
Goal - state of the system that a human wants to accomplish.
Task - activities required, used, or deemed necessary to achieve a goal.
Actions - steps required to complete the task.

7. Task Analysis
A method/set of methods for understanding the tasks users carry out with a product/system
To analyze the underlying rationale and purpose of what people are doing; what are they trying to achieve, why are they trying to achieve it, and how are they going about it?
To investigate an existing situation
Can be used for many different purposes within design and evaluation activities

9. Task Analysis Key definitions (Norman, 1988):
Goal - the state that the human wishes to achieve
Task - the activity required in order to bring about the state the human wishes to achieve (the goal)

10. Task Analysis Task analysis techniques support user-centred design
Informs us (in detail) as to:
how users use existing products
how users may interact with future products
Can be used to:
improve current design
identify potential problems with new design
identify requirements for new design
design training materials and manuals
develop evaluation plans

12. Hierarchical Task Analysis
HTA is a commonly used means of breaking tasks down into a hierarchy of goals, operations (actions) and plans
It involves breaking a task down into subtasks and then into sub – subtasks
These are then grouped together as plans that specify how the tasks might be performed in an actual situation

13. Procedure for carrying out HTA
The starting point is a user goal, then examined the main tasks associated with achieving that goal. Where appropriate, these tasks are subdivided into subtasks
Start with the overall goal (verb-noun pair), e.g. “Use ”, “Print a letter”
Break these down into meaningful sub goals/tasks (asking how question)
Break down sub goals further until reach an appropriate stopping point

14. Procedure for carrying out HTA
Add plans to the analysis - conditional statements, often utilizing Boolean logic, e.g.
DO 1, THEN 2, THEN (IF condition = true) DO 3, ELSE DO 4, THEN EXIT
Represent the goals, sub goals, operations and plans using either:
graphical views (boxes and arrows)
non-graphical methods (e.g. tabulation, outlines, textual)

15. HTA Structure Chart Notation

16. Stages of a HTA Starting the analysis Specify the main task.
Break down main task into 4-8 subtask, and specify in terms of objectives. Cover the whole area of interest
Draw out as layered plans, logically & technically correct. None should be missing.

17. Stages of a HTA Progressing the analysis
Decide on level of detail and stop decomposition. Should be consistent between tasks. Can range from detailed to high level description.
Decide if a depth first or breadth first decomposition should be done. Can alternate between the two.
Label and number the HTA.

18. Stages of a HTA Finalizing the analysis.
Check that decomposition and numbering is consistent. May produce a written account of the processes.
Have a second person look it over. They should know the tasks but not be involved in the analysis.

19. HTA – Graphical view

20. HTA – Graphical view

21. HTA – Textual representation
HTA can also be written as a list like this:
0. to clean house
1. get vacuum cleaner
2. clean rooms
2.1 clean hall
2.2 clean living rooms
2.3 clean bedrooms etc
3. empty dust bag
4. put vacuum cleaner away
Plan 0: do 1,2,4
when dust bag full, do 3
Plan 2: do any of 2.1, 2.2, 2.3 in any order depending on which rooms need cleaning.

22. An example of HTA for a Microwave Oven
What is the overall goal?
“Cook food!”
How is this done?
Prepare meal
Put meal in oven
Select programme
Listen for bell to ring
Remove meal

23. An example of HTA for a Microwave Oven
Selecting a programme - How is this done?
Set to auto sensor
Set to defrost
Set timer to cook
What are the rules that influence the order in which tasks/subtasks take place? (the plans)

24. An example of HTA for a Microwave Oven

25. Further Task Analysis (Matrixes)

26. Task Analysis – Critical thinking
Some requirements that might have ‘emerged’ from carrying out this Task Analysis:
The need for a distinctive, but not annoying, bell sound
The need for an easily accessible mechanism for opening the door
The need for a highly learnable (guessable) means of selecting a programmed

27. Assumptions about the interface
Must be made to fulfill the system requirements.
Very true if we are describing how users behave on an existing system.
Should not be made when we are designing a new system.
Don’t limit our options before we start.

28. Q &A