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