To assess the usability of any product, including Web sites, you can use any or all of several methods. We divide these methods into two major types:
- Usability evaluations, which typically do not include users working with the product
- Usability tests, which focus on users working with the product
Usability evaluation techniques require a considerable about of judgment on the part of the evaluators and usually do not include representative users. Evaluation techniques include: surveys/questionnaires, observational evaluations, guideline based reviews, cognitive walkthroughs, expert reviews, heuristic evaluations.
You can conduct a usability evaluation as soon as you have a prototype. Many usability professionals first do a usability evaluation and then follow it up with a usability test. They use the results of the evaluation to develop hypotheses about what could be serious problems and then develop the usability test around those hypotheses.
Usability Tests and Usability Evaluations
Usability tests always including test participants; usability evaluations usually do not. Usability testing is the only way to know if the Web site actually has problems that keep people from having a successful and satisfying experience.
Generally, we are not interested in what testers think will be a problem; we want it demonstrated by having one or more users actually struggle with some aspect of the site. A usability test provides an opportunity for the site to allow users to succeed, succeed with difficulty, or totally fail.
Usability Test and Evaluation Results
The results of a usability evaluation may or may not be consistent with the results of a usability test. In a usability evaluation, you are predicting the problems or successes that users will have with the Web site. A usability test with representative users tells you whether your predictions are valid.
Probably the most popular evaluation method is referred to as aheuristic evaluation. In general, this is a method for finding usability issues in a user interface by having a small number of evaluators (usually one to five) examine the interface and judge its compliance with usability principles (heuristics). The resulting observations represent the evaluator’s opinion about what needs to be improved in a user interface.