KISS  Keep it Simple Stupid. KISS was design principle noted by the U.S. Navy in 1960. It states that most systems work best if they are kept simple. Simplicity is a key goal in design.  Learnability How easy or difficult it is to learn to effectively use a system or interface.  Likert Scale  This is a survey method in which a person is asked to rate their answer on a scale. The scale could be positive to negative with a neutral score in between.  Mental Map / Mental Model  The closer the users mental model is to the functionality of the site, the higher the site's perceived usability.
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