Usabilty & unusability, examples and considerations
ἔργον ergon wok νόμoς nomoi law, rule Used for the first time on a polish newspaper Wojciech Jastrzębowski 1857 Applied to work plece design by the father of ergonomics Kennet Frank Hywel Murrell 1949 Ergonomics is sometimes defined as the science of fitting the work to the user instead of forcing the user to fit the work. However this is more a primary ergonomic principle rather than a definition. Ergonomics
Usability ISO 9241 Ergonomic requirements for office work with visual display terminals (VDTs). ISO 13407 Human-centred design processes for interactive systems. "The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use." (ISO 9241)
Multiple factors Learnability : How easy is it for users to accomplish basic tasks the first time they encounter the design? Efficiency : Once users have learned the design, how quickly can they perform tasks? Memorability : When users return to the design after a period of not using it, how easily can they re establish proficiency? Errors : How many errors do users make, how severe are these errors, and how easily can they recover from the errors? Satisfaction : How pleasant is it to use the design?