A Systematic Review of Modifications and Validation Methods for the Extension of the Keystroke-Level Model

Table 1

KLM operators and predicted execution times in seconds [6].

Type	Operator	Description	Time (s)
Physical	K	Keystroke or button press
		Best typist (135 wpm)	0.80
		Good typist (90 wpm)	0.12
		Average skilled typist (55 wpm)	0.20
		Average non-skilled typist (40 wpm)	0.28
		Typing random letters	0.50
		Typing complex codes	0.75
		Worst typist	1.20
	P	Point with a mouse to a target on a display	1.10
	H	Home hands on the keyboard or other device	0.40
	D	Drawing n straight line segments with a total length of l
Mental	M	Mental preparation for an action	1.35
System	R(t)	System response of seconds

wpm: words per minute.