Usability Evaluation
Feedback from users is particularly important because developers seldom have an intimate understanding of the user’s perspective and work practices. Initial designs should as much as possible meet user requirements.
The cost of rectifying any divergence between the design and user needs increases rapidly as development proceeds, which means that user feedback should be obtained as early as possible from prototypes and mockups.
The most effective way to get the feedback is to test with users: watch them while they try using the product for their normal tasks. Do not just demonstrate the solution to users. Ask representative users to work though typical tasks quickly and efficiently with the minimum of assistance.
Purpose of evaluation
The purpose of the evaluation may be to identify and fix any usability problems, or may be to validate the usability of a system.Evaluating mock-ups and prototypes
The most common type of usability evaluation is to improve a product by identifying and fixing usability problems. An iterative process of repeated evaluation of prototypes can be used to monitor how closely designs match user needs. The feedback is used to improve the design prior to further testing. It usually takes about a day to evaluate a system with 6 users.
Some examples of prototypes that can be evaluated are:
- Paper-based, low fidelity simulations for exploratory testing.
- Computer simulations (typically screen-based e.g., Flash™, Macromedia Director™, Visual Basic™, Java or HTML). This can simulate the user interface while sacrificing full fidelity.
- Working early prototypes of the actual product.
Validating usability requirements
In a more mature design process, requirements for user performance and satisfaction should be established and validated by usability testing. This reduces the risk of delivering a product that fails as a result of poor user performance and satisfaction. Usability testing of an existing system will provide baseline measures as input to usability requirements (i.e. objectives for human performance and user satisfaction ratings). A Common Industry Specification for Usability Requirements has been developed to support iterative development and sharing of such requirements [http://www.nist.gov/iusr].More information on designing a user-based evaluation
Detailed information can be viewed in this article about user based evaluation(PDF File 153kb).
