of the user centred design process
User Centred Design (UCD) is an approach that supports the entire
development process with user-centred activities, in order to create
applications which are easy to use and are of added value to the
Industry surveys have clearly shown that the majority of failed
projects can be attributed to incomplete or inaccurate requirements.
The biggest cost benefit that UCD can provide is by more accurately
A design changes made late in the design process will typically
cost ten times more than if identified during requirements. Making
changes to working systems will cost about one hundred times more.
Ideally UCD activities should be integrated with other development
activities. They should be planned and managed by the development
team. Over time, UCD activities will become common practice, and
existing members of the team will be able to carry them out. However,
usability skills will most probably be needed within the project
and if necessary one or more members of the team should possess
There are four important UCD principles:
- A clear understanding of user and task requirements
- Incorporating user feedback to refine requirements
- Active involvement of user to evaluate designs
- Integrating user centred design with other development
These principles have an impact on four project phases within
the development process:
Planning – how much do I do?
UCD need not be extensive or expensive. A few simple activities
early in development will significantly reduce the overall cost
of developing an acceptable system.
UCD activities should be tailored to meet the needs of an project
or organisation and take into account the relative importance of
usability in each individual situation.
- For small self contained systems, the effort required
to implement UCD would typically range from 15-50 person days
of design and evaluation expertise.
- Conduct a cost-benefit analysis or consult already
existing cost-benefit studies of projects with comparable conditions.
Analysis & Requirements – deciding
what to do
Usability is only valuable if it supports business objectives.
It is important to start by identifying and prioritising which user
issues will contribute to the success of the project.
It is also important to identify business resources and constraints
(time, money, skills and facilities) to make sure the user centred
design plan fits in.
The next step is to identify in detail who will use the system,
and how it will be used. If this information is not easily available,
field research may be needed to obtain more detail.
Usability requirements can take the form of how accurately user
complete their tasks, how long they take and how satisfied they
are. A new system should at least be as good as any existing or
competitive system or there is a significant risk of project failure.
- Define the main goals the users are to perform
- Define a comprehensive list of all tasks the users
- Prioritise tasks according to their importance (e.g.
frequency or safety).
- Define task characteristics, such as goals, time of
performing, inputs and dependencies, output, variability, frequency,
duration, time constraints, flexibility, physical and mental demands,
linked tasks, safety, criticality.
- Define and analyse tasks and sub-tasks and identify
obstacles for solving tasks.
- Identify the usage environment through usage scenarios.
- Investigate environmental characteristics including
physical and organisational
- Identify and prioritise functional requirements based
on user task and environmental requirements.
Design – making it happen
The difference between UCD and other approaches is that UCD methods
are used to develop simple models, mock-ups or prototypes on parts
or all of the designs (graphical designs, information architecture,
interaction design, information visualisation)
Prototypes are used as touch-points with users to keep checking
that design concepts and solutions are on course from a user perspective.
The risk of developing a solution that doesn’t work is thus
Usability effort should focus on providing feedback on the acceptability
to users of design solutions while they are being developed.
- Start by designing flow structure and navigation to
support main tasks.
- Produce prototypes (ranging from simple paper mock-ups
to interactive computer-based prototypes) to obtain user feedback
on the extent to which proposed solutions meet user needs. Their
use will make the potential outcome and interaction scenario more
tangible to users
- Design iterations should be evaluated from a user perspective.
This should be done early and continuously during the design process.
Design solutions are improved until requirements are met.
Evaluation – checking that designs
are on course
The most valuable form of feedback is through evaluating design
solutions with typical users.
As design solutions are assessed, feedback of results should be
fed back to the designers quickly. The objective is to improve the
design based on user feedback. Iterative design implies a process
of design, evaluation, redesign.
Evaluation activities should begin early in development and continue
in frequently througout.
- Early in development, users can be asked to step through
their tasks following a sequence of screen sketches or paper prototypes.
- If it is impossible to involve user, usability experts
may be able to evaluate designs by “walking through”
designs based on user and task goals.
- Working prototypes can be tested more formally by users
carrying out typical tasks. Task completion and task completion
rates are key factors.
- A usability lab is not always essential but it does
have the advantage that developer may watch and discuss the tests
without disturbing the user.
- When a complete prototype is available, usability requirements
for user performance and satisfaction can be tested.