Keystroke-level model: Difference between revisions

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Revision as of 16:09, 14 February 2017

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The keystroke-level model consists of six operators: the first four are physical motor operators followed by one mental operator and one system response operator:<ref>{{cite journal|last1=Card|first1=Stuart K|last2=Moran|first2=Thomas P|last3=Newell|first3=Allen|title=The keystroke-level model for user performance time with interactive systems|journal=Communications of the ACM|date=1980|volume=23|issue=7|pages=398–400|doi=10.1145/358886.358895|ref=5}}</ref>

* '''K''' (keystroke or button press): it is the most frequent operator and means keys and not characters (so e.g. pressing SHIFT is a separate K operation). The time for this operator depends on the motor skills of the user and is determined by one-minute typing tests, where the total test time is divided by the total number of non-error keystrokes.

* '''P''' (pointing to a target on a display with a mouse): this time differs depending on the distance to the target and the size of the target,<ref>{{cite journal|last1=Fitts|first1=Paul M|title=The information capacity of the human motor system in controlling the amplitude of movement|journal=Journal of Experimental Psychology: General|date=1992|volume=12147|issue=3|doi=10.1037/h0055392|ref=3|pmid=13174710|pages=381–91}}</ref> but is held constant. A mouse click is not contained and counts as a separate K operation.

* '''H''' (homing the hand(s) on the keyboard or other device): This includes movement between any two devices as well as the fine positioning of the hand.

* '''D''' (drawing (manually) n_D straight-line segments with a total length of D(n_D, l_D) cm): where n_D is the number of the line segments drawn and l_D is the total length of the line segments. This operator is very specialized because it is restricted to the mouse and the drawing system has to constrain the cursor to a .56&nbsp;cm grid.