A usability specialist evaluates the user interface, utilizing his experience of usability tests, cognitive psychology research, perceptio, user needs, platform conventions, user environment limitations etc. The target of an expert evaluation can be any device or service with a user interface, be it the final thing or a prototype.
- cost-efficient - reveals many usability problems with little expenses
- can be done in an early phase and therefore avoid implementation of costly, erroneous designs
- fast - can be done within a few working days
- reveals 50%...80% of all usability problems
- contains concrete fixes to found problems
When user interface design is ready, but can be done in any phase.