Task analysis Chapter 5. By the end of this chapter you should be able to... Describe HTA and its features Explain the purpose of task analysis and modelling.

Task analysis

Chapter 5

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

5.2 Task analysis

• Result– 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

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

5.4 Purposes of task analysis

• Purpose– 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

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

5.5.1 Inputs to and outputs of TA

• Inputs– Problem statement– Observation of existing systems– Analysis of users

• Outputs– HTA or other document, e.g. matrix– Problem statement– 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

5.5.2 Data collection

• Ask people– 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

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

5.6.1 HTA example 1:Withdraw cash from ATM

0 Withdraw cash

1 Check machine will work1.1 Look at status

indicator

1.2 Look for card logo

2 Insert card

3 Enter PIN number

4 Select Language

5 Initiate withdrawal transaction5.1 Select withdraw

cash

5.2 Specify account

5.3 Enter amount

6 Complete transaction6.1 Take card

6.2 Take cash

6.3 Take statement

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

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 orderPlan 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.

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 Select Language

5 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

5.6.2 HTA example:Plans added

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?

E2/T0: Filing cabinet

0. Store documents in filing cabinet1. File lots of documents

2. File one or two documents

Plan 0: Do 1 or 2

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.

E2/T2.2: Filing each document

2.2. 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

Plan 2.2: Do 2.2.1, 2.2.2., 2.2.3., then 2.2.4.

E2/T1: Filing lots of documentsStrategy• 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 documents1.1. Choose criteria on which documents are sorted1.2. Sort all documents to be filed into order1.3. Split documents up into categories1.4. Open cabinet1.5. Place each category of document into file1.6. Close cabinet

Plan 1: Do 1.1., 1.2., 1.3., 1.4., (1.5. repeatedly) then 1.6.

E2/T1.1:Choosing sorting criteria

1.1. Choose criteria on which documents are sorted

1.1.1. Choose alphabetical by title of document

1.1.2. Choose alphabetical by author of document

1.1.3. Choose date order

Plan 1.1: Do any one of 1.1.1., 1.1.2., or 1.1.3.

E2/T1.5:Placing categories in files

1.5. Place each category of document into file

1.5.1. Open file

1.5.2. Place each document in file

1.5.3. Close file

Plan 1.5: Do 1.5.1., (1.5.2. repeatedly) then 1.5.3.

HTA: E2 0. Store documents in filing cabinet

1. File lots of documents1.1. Choose criteria on which documents are

sorted1.2. Sort all documents to be filed into order1.3. Split documents up into categories1.4. Open cabinet1.5. Place each category of document into file1.6. Close cabinet

2. File one or two documents

2.1. Open cabinet

2.2. 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

2.3. 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, 2.2.2., 2.2.3., then 2.2.4.

E2: Things to note...

• Note …– 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?

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.

E3/T0: Example

0.Using catalogues

1. Browse items

2. Mark items

Plan 0: do 1 then 2 if item found

E3/T1: Example0. Using catalogues

1. Browse items1.1. Browse by what’s new1.2. Browse by sales1.3. Browse by items that interest1.4. Browse by catalogues

1.4.1. Browse in kitchen1.4.2. Browse while watching TV1.4.3. Browse in bed1.4.4 Browse in bath

2. Mark items

Plan 1: do 1.1 or 1.2 or 1.3 or 1.4

E3/T2: Example

0.Using catalogues1. Browse items2. Mark items

2.1. Circle item2.2. Mark page

2.2.1. Dog-ear page2.2.2. Sticky on page

Plan 2: do 2.1 or 2.2

E3/T2: Example

0.Using catalogues1. Browse items2. Mark items

2.1. Circle item2.2. Mark page

2.2.1. Dog-ear page2.2.2. Sticky on page

Plan 2.2: do 2.1.1 or 2.2.2

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

Summary

• Task analysis gives designers a means of describing how people do their jobs

• Serves different purposes in design and development