Evaluation Models
• Keystroke Level Model (Card et al. 83)
– Used previously in SMS (Dunlop and Crossan 00, Kieras 01)
– Problem: keystrokes are weighted equally
• We developed an Operation Level Model
– Similar to (Pavlovch and Stuerzlinger 04)
– Tie keystrokes to one of 13 operation types
(e.g.,
   enter a symbol = MPSymK,
   directional keypad move = MPDirK,
   press a different key to enter a letter = MPAlphaK
   press a same key to enter a letter = RPAlphaK