CS252. User Interface Design

Lecture Outline for Jan. 10
Understanding User Error

1.   Importance of Usability
     How can usability have impact on user attitude?

     How can usability affect sales of the software?

     How can usability affect workplace productivity?

     How can usability affect safety?

2.  Satisfaction vs. Performance

     Relative importance of satisfaction vs. performance
          Neilson & Levy ( "Measuring Usability - Preference vs. Performance") findings

     How to design for satisfaction 

3.   Why Users Have Problems with Interfaces
     Mack et al (1987) and Carroll & Mack (1987) established how people learn to use software and 
          what the problems are
     (1) Learning is difficult   and is personalized

     (2) Learners lack basic knowledge

     (3) Learners make ad hoc interpretations

     (4) Learners generalize from what they know

     (5) Learners have trouble following directions

     (6) Problems interact

3.   What Errors Are
     Important to understand why errors occur 

     Norman's (1981) work on errors in using software

     Two basic classes:


     Types of slips (elicit examples)
          Capture error:

          Description error:

          Data-driven error:

          Associative-activation error:

          Loss-of-activation error

          Mode error:

     What can be done to prevent slips?

     What can be done to prevent mistakes?