1. HCI Meeting 12 Tues, October 5

2. Research Project Human subjects approval

3. GOMS Models Example: Latitude, longitude and elevation Goal: Find latitude, longitude and elevation. –Question: Form of result? Operations: Methods: Selection rule:

4. Latitude, Longitude, and Elevation Example (continued) Your findings –System –Operations –Methods –Selection rule –Results

5. 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:

6. 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 scale Choice 3: Dialog box (command line), special syntax: C|F Enter

7. Temperature Conversion Choices (2) Choice 4: Dialog box (command line), special syntax: C|F Choice 5: Dialog box (command line), input integer, two outputs (one assuming input is in Celsius, one assuming input is in Fahrenheit)

8. 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

9. Information Efficiency Measure information in bits Information in choice among n equally likely alternatives is log 2 n. (Careful with definitions.) Hence, information in any one alternative is (1/n) log 2 n If n = 1, amount of information is 0

10. 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 interface

11. 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

12. Next Time Submit IRB Form