HCI by ert554898



  Meeting 12
Tues, October 5
         Research Project
• Human subjects approval
            GOMS Models
Example: Latitude, longitude and elevation
• Goal: Find latitude, longitude and
  – Question: Form of result?
• Operations:
• Methods:
• Selection rule:
Latitude, Longitude, and Elevation
Example (continued)
• Your findings
  – System
  – Operations
  – Methods
  – Selection rule
  – Results
         GOMS Models (2)
Example (Raskin, Chpt 4): Convert
  Fahrenheit to Celsius or conversely
• Goal: Temperature conversion
  – Question: Form of result? Accuracy?
• Operations: Five different sets
• Methods:
• Selection rule:
 Temperature Conversion Choices
• Choice 1: Pair of radio buttons, dialog
  box, Enter activates process
• Choice 2: Pair of sliders for direct
  manipulation, three buttons to reorient
• Choice 3: Dialog box (command line),
  special syntax: C|F <integer> Enter
      Temperature Conversion
           Choices (2)
• Choice 4: Dialog box (command line),
  special syntax: <integer> C|F
• Choice 5: Dialog box (command line),
  input integer, two outputs (one assuming
  input is in Celsius, one assuming input is
  in Fahrenheit)
      Temperature Conversion
           Choices (3)
• Basis for choosing
  – Speed: Keystroke level model
  – Keystrokes
  – Direct manipulation
  – Ease of use
  – Congruence with mental model
  – Ease of learning
  – Information efficiency
        Information Efficiency
• Measure information in bits
• Information in choice among n equally
  likely alternatives is log2 n. (Careful with
• Hence, information in any one alternative
  is (1/n) log2 n
• If n = 1, amount of information is 0
     Information Efficiency (2)
• IE = information needed by system divided
  by information required from user
• Design principle: Avoid interfaces in which
  IE = 0.
• Design principle: Maximize IE in any
    More GOMS Experiments
• Complete store purchase with credit card
• Design movie ticket vending machine
• Produce equation (4), page 86
  – Set exactly like the book
  – Set using mathematical text standards
             Next Time
• Submit IRB Form

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