Usability covers more than just "does it work?"
Usability, in the best and most comprehensive sense, refers to the total satisfaction a user derives from a product in solving a problem.
Product Usability (including web sites and software products):
1. functionality: does it actually do what it's supposed to do?
2. desirability: does it do it in a manner, speed, or style that is pleasing to the user?
3. learnability: is it easy to master the techniques required for using it?
4. memorability: is it easy to remember how to use it?
5. error recovery: is it easy to correct a mistake when using the product?
6. intuitivity: is its operation natural, logical, instinctive, possible to figure out, even if no owner's manual or training is available?
7. adaptability: can the product be altered or adjusted, within its normal functions, for my specific and unique needs?
8. reliability: can I trust the product to perform in a predictable manner?
9. virtuosity: does it seem to be the ideal solution to my needs?
10. invincibility: can I easily return to default mode, or normal operation, after a catastrophic error?
11. collectivity: can I find groups of other users of this product to learn from or to share experiences with?
12. advisability: can I access experts who will answer my technical questions?
13. elasticity: if necessary, can I use it to perform tasks that it's not specifically designed for? (e.g., using a magazine to swat a fly, or using a search engine as a dictionary to find a definition of a word).
14. auto-operability: can it be programmed to perform some functions without my personal, immediately present involvement?
15. accessibility: can the product be operated by physically challenged end users (deaf, blind, etc.), or can it be modified to accommodate them?
Associative Factors of Usability include:
16. buyability: is it in my price range, and can I purchase it by my favored method (check, money order, credit card, online payment system, etc.)?
17. deliverability: is it easy to obtain? will it come to me? or must I go get it?
18. serviceability: is it easy to fix or obtain repair work?
19. recommendability: is it worthy of suggesting that my boss, co-workers, colleagues, friends, family, or neighbors purchase it?
20. ego-compatibility: does the product somehow enhance the image I'm trying to project to others about myself?
21. extendability: is it possible to add accessories to the product, or update it somehow, so it remains compatible with upcoming products it is used in association with, thereby retaining its usefulness into the future?
Usability Analysis will attempt to answer all these aspects of a product, especially the first 15.
Of course, not all these aspects apply to every product, and some aspects will be more important than others, depending on the product and the environment in which it is used.
How NOT to Determine "Usability"
Usability is not fully determined by user reports, questionnaires, or surveys. Often users tell you what they think you want to hear, and don't want to appear ignorant or clumsy.
("It works fine" may mean "I don't want you to think I'm lazy, inept, or stupid." "I like the colors and design" may mean "I'm not an artist, so I have no idea how to evaluate these aspects, nor how they could be improved.")
Usability is not determined by the manufacturer.
Manufacturers know far more about the product than typical users, so are not in a position to realistically evaluate a product's ease of use for a typical customer. They tend to assume that if it makes sense to them, it should be transparent to everyone.
Usability is not determined by the sales staff. They may know how well a product is selling, but sales volume alone is no guarantee of usability.
Once again, they may be hearing insincere commentary, what the customers think the sales staff wants to hear. Conversely, they may be hearing an inordinate amount of complaints. Satisfied users tend to go along their merry way, not providing any feedback.
Products with poor usability, that are advertised or discounted aggressively, may sell well intially...then be returned for refunds, while disgruntled buyers spread negative word of mouth advertising against it.
Or the product is just thrown away, with customers not bothering to complain or demand refunds. Either way, sales eventually drop.
Usability is discovered only by observing users interact with the product to achieve specific, desired results.
Usability is "performance evaluation from the user's point of view."
Usability is the real "brand" of a product: what's "branded" or burned into the user's consciousness, as the user incorporates the product in their daily life.
Usability Analysts, like myself, must think long and hard about a product, view it from every possible angle, and actually watch users interact with the product in solving a problem.
See my article on "Eight Web Usability Killers" at
Click on blue underlined link (article title) above.
Or type in the URL and look under "Resources" > "Web Usability" > "Eight Web Usability Killers" at webcredible site.