user and task analysis howell istance department of computer science de montfort university

User and Task Analysis

Howell Istance

Department of Computer Science

De Montfort University

SOFT3057 - Interactive Systems

Objectives...


User Centered Design Process

Knowledge of the user as an information processor as part of an occupational

group

Knowledge of theuser’s job and it’scomponent tasks

Knowledge of the user’swork environment- organisational- physical

Knowledge of design principles- dialogue design-information presentation-graphics design

Knowledge of systems- delivery platform- I/O devices

(knowledge of how to )Produce a initial design andbuild a prototype

(knowledge of how to)evaluate and test prototype

Requirements specification-usability specification


System Related User Characteristics

What characteristics can you expect of the users of your interface? frequency of use discretion to use the system knowledge of the task which the system will support knowledge of computers experience of other similar systems general abilities, e.g. literacy, vision attitude towards computers (and your system) existing skills (keyboard, mouse)


Three-Dimensional Framework

Three Dimensional Framework for User Classification

Kno

wle

dge

of C

ompu

ters

Knowledge of Task

Frequency of Use

(low) (high)

(high)

(high)


Design implications

Provide for high degree of sophistication in interface: range of functions provided, flexibility to combine functions to provide new commands, possibilities to customise interface to own needs.

Lower requirement for user support than with other user types.

Can utilise programming languages and extensible command languages (e.g. macros and scripts).

Computer professionals


Highly variable group in terms of knowledge and

experience

Design implications Important to support the user ‘guessing’ or experimenting

with how operations can be carried out at the interface. Consistency and a close match to the user’s task model is important.

Frequency of use determines how much the user can be expected to learn short cuts and accelerators.

User support provided by the interface is important.

Professionals without programming experience


Design implications Can anticipate significant learning of routine operations to

take place, so can make use of abbreviations and codes for data input.

Can expect strong user skills to be developed, such as keyboard skills.

Error messages must be clear and provide specific guidance for recovery.

Cannot expect users to develop deeper knowledge or understanding of the computer system without specific training.

Skilled clerks


Design implications Every type of user error must be trapped. This type of

user will not be able to infer what is happening or the cause of an error condition.

Require explicit on-screen prompts for each step of the dialogue.

High degree of user support and a low degree of sophistication is required in the interface. ?

Naïve users


Task Analysis

provides an essential basis for early stages of interface design evaluation of design at early and late stages structuring training in system use structuring and design of documentation


Levels of Task Analysis

relate to existing situation or new system.

General Analysis of User Characteristics

Detailed Analysis of tasks in present job(s)

Subset of tasks to be included in new system

Analysis of Actions and Objects in new system


General Analysis level

who are the users classify the users into one or more groups define characteristics of the group

what are the main task components of the users present job what proportion of time is spent in different tasks what causes variations in this

where are the tasks carried out what equipment (other than the computer system)

are used what communication is there between the user and

other people


Detailed analysis of tasks in present job

what is the hierarchical structure of main tasks, and subtasks within these main tasks

how do users see the structure of their job in terms of tasks for each task identified

what information is required what actions arise or result from decisions what feedback is provided on effect of actions what affects successful performance what are the possible errors and what factors cause these


Detailed analysis of tasks in present job

what are the good features of the existing system which should be retained in the subsequent redesign

what are the bad features of the existing system that should be designed out

what skills are required for each task how are the required skills trained initially and how are

these retained


Actions and Objects

Low level (down the hierarchy) task descriptions can be formulated as actions performed on task-related objects e.g... change start time of appointment object: appointment attribute: start time action: change/edit

a dictionary of objects, attributes and associated actions can be constructed through process of rationalisation generification


Building an object dictionary

interviews with users provide textual descriptions of tasks these can be analysed by identifying

nouns (candidate objects) verbs (candidate actions)

process of generification to identify what are essentially descriptions of the same thing

process of hierarchy building to identify objects as members of related classes


Objectives of task analysis to support interface design

identify a hierarchy of user goals, tasks and subtasks together with a plan describing how and when these are done

represent lowest level task as a set of procedures (using something like pseudocode) include statements of information requirements and exception

conditions identify set of actions and associated objects


Hierarchical task analysis (HTA)

Originally devised to define training requirements in process industry - method needs additionally descriptions of information requirements for lowest level sub-

operations dictionary of objects and associated actions

Representation tree diagram or tabular format

Advantages of HTA simple, informal notation but still requires considerable skills on part of analyst.


Example of HTADelete block of text in a word processor

1.Deleteblock of text Goal


Example of HTADelete block of text in a word processor

1.Deleteblock of text Goal

2) Select 'cut' from Edit menu

1) Select block of text

or 2) Select cut icon from toolbar

or 2) Press 'delete' key

then

Tasks


HTA representation

1.Deleteblock of text

1. Selecttext block

2. Press‘delete’

3. Select cutfrom edit menu

4. Select cut iconfrom toolbar


HTA representation


1. Selecttext block




Plan 1: 1-2 or 1-3 or 1-4


HTA representation


1. Selecttext block




Plan 1: 1-2 or 1-3 or 1-4

1) Anchor the start of the block2) adjust the extent of the block

3) Anchor end of the block

then

then

Subtasks


HTA representation of tasks and subtasks


1. Selecttext block




1.Define start of textselection

2. Adjust lengthof text selection

3. Define end oftext selection

Plan 1: 1-2 or 1-3 or 1-4

Plan: 1.2 1-2-3


HTA representation of tasks and subtasks


1. Selecttext block







Plan 1: 1-2 or 1-3 or 1-4

Plan: 1.2 1-2-3

Procedure

1) position text insertion in front of first character of block2) ...


How far to decompose tasks?


1. Selecttext block







Plan 1: 1-2 or 1-3 or 1-4

Plan: 1.2 1-2-3


How far to decompose tasks?


1. Selecttext block







Plan 1: 1-2 or 1-3 or 1-4

Plan: 1.2 1-2-3

.. as far as is useful for the analysis


Means of collecting task analysis data

interviews with potential users observations of users performing tasks by trained

observers activity sampling activity logging (by observer) activity logging (by user) - 'diary of activities'

user and task analysis howell istance department of computer science de montfort university

Documents

n user support

system u knowledge

n frequency of use

new system slide

n high degree of user

u flexibility

u possibilities

user types