UNDERSTANDING UNDERSTANDING TASK ANALYSISTASK ANALYSIS

NIK ISROZAIDI NIK ISMAIL

Learning outcomes

At the end of this lecture, you should be able to: Draft the Hierarchical Task Analysis (chart

or textual based)

Key terms

Task analysis Hierarchical task analysis

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

Task - Decomposition

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.

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

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)

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

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

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 email”, “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

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)

HTA Structure Chart Notation

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.

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.

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.

HTA – Graphical view

HTA – Graphical view

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.

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

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)

An example of HTA for a Microwave Oven

Further Task Analysis (Matrixes)

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

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.

Q &A