Upload
buidan
View
215
Download
0
Embed Size (px)
Citation preview
4
Problem Statement• Goal– Develop simple model to describe time to do task with a
given method on an interactive system• Ttask = Tacquire + Texecute
whereTtask = total time to complete taskTacquire = time to select method to complete taskTexecute = time to perform method
• Model predicts Texecute• Assume expert users and no errors
5
Model
• Texecute = ∑(time to execute primitive op)
• Primitive operations– K key/button press– P point to target with mouse– H home hands to keyboard or mouse– D draw line with mouse–M mental preparation (pause)– R system response time
6
Model (cont.)
• Times for primitive operations are predicatedfrom experiments– Time to press key/button ranges between• 0.08 sec/char fast typist• 0.28 sec/char average typist• 1.2 sec/char slow typist
8
Encoding Method• Code method as sequence of primitive operations,
sum up times• Example: replace 5 letter word with another• Editor 1: keyboard based
– next line MK[(line feed)]– substitute command MK[s]– enter new word 5K[xxxxx]– terminate arg MK[(return)]– enter old word 5K[zzzzz]– terminate arg MK[(return)]– terminate command K[(return)]
• Texecute = 4tM + 15tK = 8.4 sec
9
Placement of M’s
rule 0: place M before all K’s not part of arg strings and beforeall P’s that select commands
for each M do
rule 1: if operator fully anticipated, delete M(e.g. PMK → PK)
rule 2: if string of MK’s belongs to cognitive unit, delete all M’s but firstrule 3: if K is redundant terminator, delete Mrule 4: if K terminates constant string (i.e. command), delete it
if K terminates variable string (i.e. arg), keep it
1 0
Placement of M’sExample: Mouse-based Editor 2 sequence
H[m]P[word]K[y]H[k]K[R]5K[…]K[(esc)]
⇒H[m]P[word]MK[y]H[k]MK[R]5K[…]MK[(esc)]
⇒ H[m]P[word]K[y]H[k]MK[R]5K[…]MK[(esc)]
M M M
delete
rule 0:
rule 1:
1 1
Placement of M’s
Example: Keyboard-based Editor 1 sequence
K[(lf)]K[s]5K[…]K[(ret)]5K[…]K[(ret)]K[(ret)]
⇒ MK[(lf)]MK[s]5K[…]MK[(ret)]5K[…]MK[(ret)]MK[(ret)]
⇒ MK[(lf)]MK[s]5K[…]MK[(ret)]5K[…]MK[(ret)]K[(ret)]
M M M
delete
rule 0:
rule 3:
M M
1 2
Empirical Validation
• Conducted experiment on real systems tocompare predictions to observations
• 14 tasks on 3 types of systems– text editors– graphics systems– command executers
• Users– practice using system– were tested to determine typing and drawing speed
Some Recent Applications of the KLM
• Balter, O. (2000). Keystroke level analysis of email message organization.Proceedings of the ACM Conference on Human Factors in ComputingSystems – CHI 2000 105-112. New York: ACM
• Dunlop, M. & Crossan, A. (2000). Predictive text entry methods formobile phones. Personal and Ubiquitous Computing 4, 134-143.
• Holleis, P., Otto, F., Hussmann, H., & Schmidt, A. (2007). Keystroke-level model for advanced mobile phone interaction. Proceedings of theACM Conference on Human Factors in Computing Systems – CHI 2007,1505-1514. New York: ACM.
• Pettitt, M., Brunett, G. & Stevens, A. (2007). Anextended keystroke level model (KLM) forpredicting visual demand on in-vehicleinformation systems. Proceedings of the ACMConference on Human Factors in Computing Systems– CHI 2007, 1515-1524. New York: ACM.
1 4
The KLM and Text Entry
• The KLM and Text Entry– The original experiment did not include a task
such as:– Enter a 43-character phrase of text
• Why?– It’s too simple for the KLM– Prediction reduces to 43 x tK– tK determined for each user in a pre-test– The KLM task just confirms the pre-test
1 5
Model for T9 Entry of “beep”
M P – t h e t i m e f o r p e r f o r m i n g a p h y s i c a l m a t c h
b e t w e e n a s t i m u l u s ( t h e p r e s e n t e d
w o r d ) a n d a c o d e s t o r e d i n t h e u s e r ' s
s h o r t - t e r m m e m o r y ( t h e d e s i r e d w o r d ) .
1 7