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GOMS and keystroke predictive methods

Judy Kay CHAI: Computer human adapted interaction research group School of Information Technologies. GOMS and keystroke predictive methods. Overview. Predictive methods GOMS and keystroke analyses Benefits Disadvantages Adapting GOMS to Pervasive Computing

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GOMS and keystroke predictive methods

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  1. Judy Kay CHAI: Computer human adapted interaction research group School of Information Technologies GOMS and keystroke predictive methods

  2. Overview Predictive methods GOMS and keystroke analyses Benefits Disadvantages Adapting GOMS to Pervasive Computing (>1 million Google matches)‏

  3. Postconditions for this week (incl private study)‏ Describe the uses of GOMS Describe the processes for conducting GOMS analyses Describe advantages and limitations Ability to perform a GOMS study on conventional interfaces and explore the approach for pervasive systems Justify the use of GOMS in the overall testing of a pervasive computing application

  4. GOMS Goal Operations - keystrokes, clicks Methods - sets of operations Selection rules - decide between methods For expert users

  5. GOMS example (Newman and Lamming)‏ Make "the cat" bold in "the cat sat on the mat" Goal - to make "the cat" bold Operations - keystrokes, clicks Methods - ctrl-b or mouse/menu Selection rules - which method?

  6. K - keypress P - point with mouse C - click with mouse H - home hands on new device M - mentally prepare R(t) - system response time

  7. K – keypress .08 - 1.20 P - point with mouse .8 - 1.5 (Fitt's Law)‏ C - click with mouse .2 H - home hands on new device .4 M - mentally prepare 1.35 R(t) - system response time ? How would you determine values for a pervasive system?

  8. NOTES: M before K/C or P except PMK ... PK if K “anticipated” e.g. move mouse to target and click MKMKMK ... MKKK for cognitive unit e.g. type “cat”

  9. Method 1 – highlighting “the cat” Assumptions: hands were on keyboard and R = 0. H - 0.40 - Reach for mouse M – 1.35 – mentally prepare P - 1.10 - Point to the left of "the" C - 0.20 – Click mouse M – 1.35 – mentally prepare P - 1.10 - Point to right of "cat" C - 0.20 - Release mouse Total = 5.7

  10. Method 1 cont – bolden keyboard shortcut M – 1.35 – mentally prepare K - 0.60 - Press and hold "Control" K - 0.60 - Press "B" K - 0.60 - Release "Control" Total = 3.15

  11. Method 2 - use menu Assumptions: hands were on keyboard and R = 0 M – 1.35 – mentally prepare P - 1.10 - Point to "Format" menu C - 0.60 - Click and hold M – 1.35 – mentally prepare P - 1.20 - Point to "Bold" menu item C - 0.60 - Release mouse Total = 6.2

  12. Conclusion for this case Assumtions: Hand position, R, K, P Common part is 5.7 (sweeping out “the cat”)‏ Rest of Keyboard shortcut takes 3.15 seconds Mouse menu method takes 6.2 seconds

  13. Summary of approach Focus on speed Known sequence of operations Can predict performance for experienced users Walkthrough steps, calculate time for each step, sum Can sometimes predict choices of method

  14. Summary of uses Relatively inexpensive Can be used to compare “methods” Challenging to apply for conventional interfaces .... pervasive? Expert users only Would you expect software that assist in this?

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