Task Analysis
Summer 2013
5.1 Introduction
• In the last chapter we looked through the
UCSD process.
• We identified TA as an important part of
the system design.
• In this chapter, we will explore how to use
it in system design and evaluation.
5.2 Task Analysis
• The result of TA is a description of the tasks
that users undertake when interacting with a
system.
• It also involves how individuals carry out these
tasks.
• The typical use of TA is to describe an existing
system or task before serious design work starts
on a new system to replace it.
5.2 Task Analysis (Cont.)
• The aim of TA is to find out what the old system enables
users to do, so that the designers can understand what
is required of the new system.
• A description of existing user tasks enables the
designers to review those tasks – and hence to redesign,
re-implement or remove them from the new system.
• Note: the analysis should inform the development of the
new system, not constrain it. Following a development
method is not a substitute for innovation.
5.2 Task Analysis (Cont.)
• TA is very useful when it comes to designing a ‘walk-up-and-use’
system, such as a ticket booking or new phone system.
• For the ‘walk-up-and-use’ system you don't want to have to retrain
the public to use your system: it should be as natural to use as
possible.
• Therefore, it is crucial to understand what tasks users carry out and
how they carry out those tasks with the old system.
• The main failure of the ticket booking system (ch.1): it imposed an
unnatural task structure on its users and didn’t support some subtle,
but very important, tasks that users engage in when booking tickets
with a human representative.
5.2 Task Analysis (Cont.)
• This chapter will go in detail as to how to
gather appropriate information to conduct
a TA, and at notation for recording the
results of a TA.
5.3 What Is Task Analysis?
•
TA provides a means of analyzing and describing the jobs & tasks that
people do so that they can be supported by interactive computer systems.
•
TA provides both a method of analysis & notation to capture the results.
•
The focus is on people’s goals & the actions they carry out to achieve those
goals.
•
The task is broken down into a set of related actions.
•
The analysis includes the skills and abilities that people need to have to
perform a task and the things that they act on while doing so.
•
TA structures: hierarchy and structures (matrices & grids) are sometimes
more appropriate.
5.4 Purposes of Task Analysis
•
The purpose of TA is to help designers to understand existing systems,
tasks, necessary skills encountered and people’s existing jobs.
•
The aim is to contribute to a better understanding of the requirements that
users have of a system.
•
In this way, TA can be very useful in evaluating the design of an existing
system or in developing the design of a new system.
•
It might also trigger an insight into how to do a task better. Ex, before the
development of spreadsheet, Dan Bricklin, studying at Harvard Bus. School,
wanted a system for performing large, complex financial calculations without
having to write a new program or re-enter the data each time. Harvard
Professor used rows and columns to enter data: idea triggered to build a
system that automatically updates equations in all related cells.
5.5 Approaches to Task Analysis
• TA approaches: Hierarchical Task Analysis (HTA) &
Procedural Task Analysis (PTA).
• Some task structures many not be hierarchical in form –
so do not force all tasks into the same shape.
• PTA:
– it involves following a sequence of activities to achieve a goal.
– All activities are executed in a step-by-step, linear and sequential
manner.
– Its directional flow has a start & an end
– A proceeding task must be completed before beginning a new
task.
– A PTA can easily be represented in the form of a flowchart
diagram.
5.5 Approaches to Task Analysis
• Generally TA involves a focus on:
– Goals & actions (procedures/methods) that
users carry out.
– What users know about their work & tasks.
– The psychological process such as perception
and memory
– Objects and entities on which users act.
– Objects and attributes on how they are
related.
Inputs & Outputs to Task Analysis
• Inputs to TA:
– Problem statement
– Observations of the existing system
– An analysis of your users
• Outputs to TA:
– HTA
– TA based upon other structures (ex, matrix)
– The problem statement: Ex, design a new sys. For online
shopping
– Observation of existing systems: find the good and bad of the
system & evaluate it using the Jacob Nielsen's heuristics.
– Analyze and profile the user population: ID the people who will
use you system.
Other Issues to Consider
• Who are the users? Can you produce a profile of the group of
people who will be your users?
• How diverse is your user population? Are you unintentionally
excluding some? How would you know?
• How could you improve your design so as to provide universal
access? How can your designs be inclusive (general)?
• Why don’t people use the system? Ask them why they don’t use
it. What changes would makes them want to use a new version.
What do they do?
• Observe goals as well as tasks.
Data Collection
•
Collecting data about the tasks the people perform is more difficult than
what it seems.
•
Data collection methods to consider:
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•
Observe user working
Talk to them informally, in focus groups or interviews
Read available documentation or training materials
Do the task yourself
Familiarize yourself with the existing system
Analyze real tasks
Develop abstractions of real tasks
Conduct experiments
Conduct surveys
Explore the context in which tasks are done
TA is about gathering and analyzing reliable data.
5.6 Hierarchical Task Analysis
• HTA is one of the most common forms of TA.
• It involves:
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identifying the goals that users want to achieve
breaking down (decomposing) goals into tasks
further decomposing into sub-tasks
and repeating this decomposition until you reach the level of actions.
• The level of detail can be subjective, but it is usually clear in
practice.
• The fundamental rule is that the task can be depicted naturally as a
hierarchy.
HTA Ex: Withdrawing Cash from an ATM machine
• Withdrawing cash from an ATM requires tasks from the user...
• What are those tasks?
HTA Ex: Withdrawing Cash from an ATM machine
0 Withdraw cash
1 Check machine will work
1.1 Look at status indicator
1.2 Look for card logo
2 Insert card
3 Enter PIN number
4 Initiate withdrawal transaction
4.1 Select ‘withdraw cash’
4.2 Enter amount
5 Complete transaction
5.1 Take card
5.2 Take cash
5.6 Hierarchical Task Analysis
• Adding Plans to and HTA:
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How sub-tasks are combined
The order in which they are used
Conditional or optional sub-tasks
Any repetition required if involved
• For Example:
Plan 0: do 1; if possible do 2; repeat 3 until PIN correctly entered;
do 4; do 5
Plan 1: do 1.1, 1.2 in any order
Plan 4: do 4.1; then do 4.2.
Plan 5: wait until card available; do 5.1; wait until cash available;
do 5.2.
5.6 Questions about HTA
• How can we improve these TA? What does the example tell us
about HTA and the UCSD?
• Clearly, in most cases we will need to create a flexible and
interactive system. Portability is often an important requirement, in
terms of both location and hardware.
• Key features of an interactive system based on HTA include:
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Flexibility
Interactivity
Portability (location and hardware)
Flexible browsing capability
Suitable functionality
Different Approaches to TA
HTA based on a matrix representation
In order to cook
A boiled egg
You need to obtain
An egg
water pan heat
A fried egg
An egg
oil
pan heat
Chinese meal
Ingredients* oil
pan heat
*Chinese cabbage, spring onion, rice, noodles
Different Approaches to TA
HTA for boiling an egg
To boil an egg
Obtain resources
heater
egg
water
pan
Transform egg
Boil water
Boil egg
Different Approaches to TA
HTA for cooking items
Cook
Boil water
prepare
Boil egg
boil
prepare
boil