Overview 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 intended users.
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 defining requirements.
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 these skills.
There are four important UCD principles:
- A clear understanding of user and task requirements
- Incorporating user feedback to refine requirements and design
- Active involvement of user to evaluate designs
- Integrating user centred design with other development activities
These principles have an impact on four project phases within the development process:
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.
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 will perform
- 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.
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 minimised.
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.
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.