© De Montfort University, 2001 1

Users and User Characteristics

Howell Istance

Department of Computer Science

De Montfort University

© De Montfort University, 2001 2

Contents

• Users - Designing for diversity

• Characteristics of users

• Preece, Chapters 2, 17 and 18– In particular read Ch. 17 - two examples of user-centred design.

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Recap – Designing for usability

• Designing usable systems requires us to have knowledge of:– The users who will use the system.

– The tasks for which it will be used.

– The environment in which it will be used.

• So designers need knowledge of:– The physiological and psychological capabilities of the user.

– The types of tasks that users will be expected to carry out.

– The organisational and environmental aspects of the user’s task.

– The technical constraints of the system.

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Designing for Diversity

• The wide range of human abilities, backgrounds, motivations, personalities and intelligence presents major challenges for interactive system designers.

• They need to have an understanding of:– physical characteristics

– cognitive and perceptual abilities

– personality differences

– general abilities

• These are all characteristics which apply to people in general, we shall also consider characteristics which apply specifically as potential system users.

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Physical Characteristics

• Think of a car and its interface (controls).

What physical aspects need to be considered?

• Basic data about human dimensions comes from anthropometry.– What is average?

– What compromises must be made?

– e.g. keyboard spacing. mouse size and shape.

– Adjustments to interface, e.g. brightness of VDUs.

• These aspects of the physical design of workstations is part of Ergonomics.

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Differences between user groups…

• Consider the design of a check-out system for a large supermarket and the design of a counter system for a high-street building society

• Talk to the person next to you and make a list of some of the differences between the groups of people who will use each system

• List also how these differences could affect design decisions about each system

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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)

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Some Design Implications

• frequency of use: amount of skill building that takes place and knowledge user can be expected to retain

• discretion to use the system: impact of poor usability• knowledge of the task which the system will support: level of support

at interface provided for how to complete tasks• knowledge of computers: level of guidance provided• experience of other similar systems: user expectations and use of

familiar interface conventions• general abilities, e.g. literacy, vision: assumptions made about

presentation of text and use of other modalities• attitude towards computers: level of help and guidance and way in

which system is introduced to users • existing skills (keyboard, mouse): choice of interaction style to use to

exploit existing skills

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Categorisation of Users

• We shall consider two main ways of categorising users:– occupational categories

– level of expertise• task expertise

• computer expertise

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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)

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Occupational Categorisation of Users

• Broad occupational classification as:– computer professionals

– professionals without programming experience

– skilled clerks

– naïve users

– special groups

• Remember the first four of these are broad classifications - make sure you understand your particular user group(s).

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Computer professionals

• Classification:– computer knowledge - high/very high

– task knowledge - high

– frequency of use - high

• Understand software and hardware.

• Intelligent, well-educated and highly motivated (often).

• May want to customise software for own needs.

• Have little patience, like rapid response in software.

• Sensitive to shortcomings in software.

NOT typical of the majority of users

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• 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).

Design implications

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Professionals without programming experience

• Classification:– computer knowledge - low/moderate– task knowledge - high– frequency of use - high

• Use computer packages frequently as part of their work• Probably have not read any documentation.• Have high expectations of performance and expect to be

able to use new applications quickly with a minimum of learning

• Intolerant of software errors or poor design.• High degree of usability is critical for this group

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• 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.

Design implications

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Skilled clerks

• Classification:– computer knowledge - low– task knowledge - high– frequency of use - high

• May use a machine several hours a day.• Develop very strong user skills.• Do not have a high degree of computer sophistication.• Want rapid responses in software.• Quickly grow impatient with features designed for

less experienced users if these features slow them down.

• Usage is not usually discretionary.

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• 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.

Design implications

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Naïve users

• Classification:– computer knowledge - very low– task knowledge - varies, low - moderate– frequency of use - assume low

• Know (nearly) nothing about computers.• Cannot assume significant learning process, i.e. each

interaction with the system should be treated as if it were the user’s first.

• May feel intimidated by using a computer.• Ease of learning is important usability criterion.• Use of system is usually discretionary.

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• Can not assume familiarity with Windows objects, scrollbars, mouse, spin boxes etc.

• 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.

?

Design implications

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Special groups

• Users with physical impairments– primary concern is use of appropriate input and output devices,

matching the modality used to an individuals ability and the effort required to use the devices.

• Users with Learning difficulties– primary concern is matching content and interaction to ability

• Children– Retaining attention,

– Matching content and means of interaction to ability

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Types of Knowledge

• Syntactic (computer) knowledge - knowledge of low-level mechanisms required to achieve a particular state.– How to select a printer in a print dialog box

– How to open an application from the desktop

– Frequently used commands - e.g. Alt F S to save a file in many Windows applications

• Semantic (computer) knowledge about concepts or entities associated with the computer system.– e.g. organisation of the file system, access rights to files,

components of WWW sites

• Semantic (task) knowledge about concepts or entities associated with the task to be performed.– e.g. parts of a car design in CAD, or data requirements in statistics.

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Simple categorisation of users

• Novice users– no syntactic knowledge, little semantic knowledge

– may have little task knowledge

– may have anxieties about computer use

• Knowledgeable intermittent users– can maintain semantic knowledge of task and computer concepts

– requirements for consistency of structures in interaction so that user inferences are supported

– good help facilities and documentation are required

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Simple categorisation of users

• Frequent users– well trained in semantic and syntactic aspects

– rapid response time

– brief feedback

– abbreviated command sequences

– accelerators to move through dialogue sequences