The 5 Levels of Usability Assessment

Following the practice of Dr. Robert Bailey of Computer Psychology, Inc., we use up to 5 levels of Usability Assessment, depending on the project. These levels of assessment range from a simple Usability Review to a full-blown scientifically controlled comparison of two products or two versions of a single product.

Level 1 Inspection : review by two experts against common usability rules of thumb (i.e. 'heuristics')

Usability Inspection is used to make a quick assessment of the quantity and magnitude of commonly-observed usability problems. Because actual users or consumers are not part of Usability Review, it must never be the sole criterion on which the goodness of a product is based.

It is critical to keep in mind at all times, that real users always turn up surprises that are missed by the Reviewers.

Level 2 Expert Review: review by at least 4 experts against a comprehensive list of usability guidelines

Expert Review is used to make a quick assessment of the quantity and magnitude of commonly-observed usability problems. Because actual users or consumers are not part of Expert Review, it must never be the sole criterion on which the goodness of a product is based.

It is critical to keep in mind at all times, that real users always turn up surprises that are missed by the Experts.

Level 3 Expert Review: review by 12 -16 (combination of usability experts and domain experts). The larger number of reviewers allows statistically valid assertions (but still preliminary) to be made about the product.

Level 4 Usability Test: formal test involving 12–16 actual or potential users

Level 5 Usability Test: A scientific comparison of two versions or two different products