Principles of User Centred Design Howell Istance

Some definitions n Human-Computer Interaction u a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of the major phenomena surrounding them n User Interface u any boundary between the human user and the computer system (includes documentation and training material) u not restricted to screens, keyboards and mice

User Centered Design n all systems need not be designed to suit everyone... n.... but should be designed around the needs and capabilities of those people who will use them usability - concerned with making systems easy to learn, easy to use and efficient to use

Think about a car... n how much knowledge about a car do you to be able to drive it? n do the best designed cars give the driver the most information about the engine, suspension, etc? n good design of the interface to the car includes designing controls that are F obvious to use F behave in the way you expect F give fast feedback F are comfortable to use F hide unnecessary information from the user

Misconceptions about user interface design n a usable system has lots of functions n ‘I know it’s a bit hard to use but it’s all described in the Help system’ n ‘I know it works - I’ve got the people in the office (or on the course) to use it’

Visibility, mapping and affordance n visibility: the correct parts must be visible, they must convey the correct message - that message is conveyed by signals n mapping: the relationship between what you want to do and what appears to be possible - good design exploits natural and easily perceived mappings n affordance: the perceived and actual properties of a thing, primarily those fundamental properties that determine just how the thing could possibly be used

Perspectives on design n think ‘design first, implementation second’ n design the interface first for usability, only compromise in the design for ease of implementation later if necessary n think how the system and interface should support what the user wants to do, rather than what the system is capable of doing

Implications for the design process n early focus on users and tasks n clear understanding of what particular usability attributes are important n testing of prototypes of the design from an early stage in the process n results from prototype testing need to be used to modify the design, which is retested n software tools are needed to support this process - to enable designs to be built and modified with little programming overhead

Waterfall model of S/W development n certainly better than no model at all, but too rigid n requirements change during design process n testing occurs late in the process requirements analysis & definition System and software design implementation and unit testing integration and system testing operation & maintenance

Prototyping Model of S/W development requirements definition quick design build prototype evaluate and refine requirements engineer product

Prototyping Model of S/W development Advantages n evaluation at an early stage n prototype can be used to explore further requirements Disadvantages n quick design may be badly founded n building prototypes may not necessarily be rapid

Components in a user centred design Product requirements (including usability specification)

Usability Specifications n Usability - extent to which application is easy to learn, easy to use and efficient to use n specification - defining what constitutes success in terms of measurable quantities n e.g ‘90 % of first-time users (without prior training) will be able to retrieve the shelf number of a given book within 300% of the time it would take an expert user to do so’ (possible example from a library information system)

Knowledge of users - general psychology -characteristics of user groups Product requirements (including usability specification)

Users n Subject of next lecture

Knowledge of users - general psychology -characteristics of user groups Knowledge of users’ tasks and information requirements Product requirements (including usability specification)

Tasks n Task Analysis involves study of the work users do, the component tasks within this and the information needed to complete each task n Object of interface design is to fit the design (content, navigation) around these task needs n Several different methods of capturing this n Important to represent the analysis so that its correctness maybe checked with groups of users

Knowledge of users - general psychology -characteristics of user groups Knowledge of users’ tasks and information requirements Knowledge of environment in which application will be used Product requirements (including usability specification)

Environment n In general terms this refers to the physical and organisational environment n physical - location (e.g home, railway station, public libray) and the constraints this places on design solutions n organisational - usually an issue when introducing systems into businesses - systems need to fit the way in which they will be used

Knowledge of users - general psychology -characteristics of user groups Knowledge of users’ tasks and information requirements Knowledge of environment in which application will be used Product requirements (including usability specification) Knowledge of design principles - HCI, graphics, typography

Design principles n Important to know what design guidance is available and use what is already known n design can not proceed by recipe, principles of good practice can be given to the designer who needs to apply these u HCI principles - quality of user-computer dialogue u Graphics Design - means of effective and aesthetic visual communication u Typography - effective and aesthetic use of style in text

Knowledge of users - general psychology -characteristics of user groups Knowledge of users’ tasks and information requirements Knowledge of environment in which application will be used Product requirements (including usability specification) Knowledge of design principles - HCI, graphics, typography Knowledge of delivery platform and I/O devices

Knowledge of users - general psychology -characteristics of user groups Knowledge of users’ tasks and information requirements Knowledge of environment in which application will be used Product requirements (including usability specification) Knowledge of design principles - HCI, graphics, typography Knowledge of delivery platform and I/O devices Produce prototype

Prototypes n Early prototypes usually paper-based, used to quickly capture ideas n Later prototypes built on a machine to give a realistic ‘mock-up’ of what the final application will look like u Should have sufficient functionality to enable interactive testing before final version is available

Knowledge of users - general psychology -characteristics of user groups Knowledge of users’ tasks and information requirements Knowledge of environment in which application will be used Product requirements (including usability specification) Knowledge of design principles - HCI, graphics, typography Knowledge of delivery platform and I/O devices Produce prototype Evaluate prototype though structured testing

Evaluation n ‘expert’ based appraisal based on walk- throughs of the design in the context of completing selected tasks n subject based testing where people representative of the user population are observed completing selected tasks with the prototype n emphasis as much on qualitative data as on quantitative data