Keystroke-level model: Difference between revisions

Revision as of 08:06, 3 January 2016

Revision as of 15:05, 7 April 2016

Line 1:

TheIn Keystroke[[human&ndash;computer interaction]], the '''keystroke-Levellevel Modelmodel''' ('''KLM''') predicts how long it will take an expert user to accomplish a routine task without errors using an interactive computer system.<ref>{{cite journal|last1=Card|first1=Stuart K|last2=Moran|first2=Thomas P|last3=Allen|first3=Newell|title=The keystroke-level model for user performance time with interactive systems|journal=Communications of the ACM|date=1980|volume=23|issue=7|pages=396–410|doi=10.1145/358886.358895|ref=1}}</ref> It was proposed by [[Stuart K. Card]], [[Thomas P. Moran]] and [[Allen Newell]] in 1980 in the ''[[Communications of the ACM]]'' and published in their book "''The Psychology of Human-Computer Interaction"'' in 1983, which is considered as a classic in the HCI field.<ref>{{cite web|last1=Sauro|first1=Jeff|title=5 Classic Usability Books|url=http://www.measuringu.com/blog/usability-books.php|website=MeasuringU|accessdate=22 June 2015|ref=7}}</ref><ref>{{cite web|last1=Perlman|first1=Gary|title=Suggested Readings in Human-Computer Interaction (HCI), User Interface (UI) Development, & Human Factors (HF)|url=http://hcibib.org/readings.html|website=HCI Bibliography : Human-Computer Interaction Resources|accessdate=22 June 2015|ref=8}}</ref> The foundations were laid in 1974, when Card and Moran joined the [[PARC (company)|Palo Alto Research Center]] (PARC)]] and created a group named Applied Information-Processing Psychology Project (AIP) with Newell as a consultant aiming to create an applied psychology of human-computer interaction.<ref>{{cite book|last1=Card|first1=Stuart K|last2=Moran|first2=Thomas P|last3=Newell|first3=Allen|title=The Psychology of Human-Computer Interaction|date=1983|publisher=L. Erlbaum Associates Inc|___location=Hillsdale|isbn=0898592437|pages=ix-x|ref=4}}</ref> The KLMkeystroke-level model is still relevant today, which is shown by the recent research about mobile phones and touchscreens (see [[#Adaptions|Adaptions]]).

== Structure of the Keystrokekeystroke-Levellevel Modelmodel ==

The Keystrokekeystroke-Levellevel Modelmodel 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=121|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.

Line 26:

|}

* '''R''' (response time of the system): the response time depends on the system, the command and the context of the command. It only used when the user actually has to wait for the system. For instance, when the user mentally prepares (M) for executing his next physical action only the non-overlapping part of the response time is needed for R because the user uses the response time for the M operation (e.g. R of 2 seconds – M of 1.35 seconds = R of .65 seconds). To make things clearer, Kieras <ref name=Kieras>{{cite web|last1=Kieras|first1=David|title=Using the Keystroke-Level Model to Estimate Execution Times|url=http://www-personal.umich.edu/~itm/688/KierasKLMTutorial2001.pdf|accessdate=22 June 2015|ref=9|page=3}}</ref> suggests the naming waiting time (W) instead of response time (R) to avoid confusion. Sauro suggests taking a sample of the system response time.<ref>{{cite journal|last1=Sauro|first1=Jeff|editor1-last=Jacko|editor1-first=Julie A|title=Estimating productivity: Composite operators for keystroke level modeling|journal=Human-Computer Interaction. New Trends: Proceedings of the 13th International Conference (LNCS)|date=2009|volume=5610|page=355|doi=10.1007/978-3-642-02574-7_40|ref=10|publisher=Springer-Verlag|___location=Berlin Heidelberg}}</ref>

The following table shows an overview of the times for the mentioned operators as well as the times for suggested operators:

Line 81:

== Limitations ==

The Keystrokekeystroke-Levellevel Modelmodel has several restrictions:

* It measures only one aspect of performance: time,<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=400|doi=10.1145/358886.358895|ref=21}}</ref> which means execution time and not the time to acquire or learn a task <ref>{{cite book|last1=Card|first1=Stuart K|last2=Moran|first2=Thomas P|last3=Newell|first3=Allen|title=The Psychology of Human-Computer Interaction|date=1983|publisher=L. Erlbaum Associates Inc|___location=Hillsdale|isbn=0898592437|pages=260–261|ref=22}}</ref>

* It considers only expert users. Generally, users differ regarding their knowledge and experience of different systems and tasks, motor skills and technical ability <ref name="klm-paper-limitations-users">{{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=397, 409|doi=10.1145/358886.358895|ref=23}}</ref>

* It considers only routine unit tasks <ref name="klm-paper-limitations">{{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=409|doi=10.1145/358886.358895|ref=24}}</ref>

* The method has to be specified step by step<ref name="klm-paper-limitations" />

Line 89:

* The mental operator aggregates different mental operations and therefore cannot model a deeper representation of the user’s mental operations. If this is crucial, a GOMS model has to be used (e.g. model K2)<ref>{{cite book|last1=Card|first1=Stuart K|last2=Moran|first2=Thomas P|last3=Newell|first3=Allen|title=The Psychology of Human-Computer Interaction|date=1983|publisher=L. Erlbaum Associates Inc|___location=Hillsdale|isbn=0898592437|pages=285–286|ref=25}}</ref>

Also, one should keep in mind when assessing a computer system that other aspects of performance (errors, learning, functionality, recall, concentration, fatigue, and acceptability),<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=396–397|doi=10.1145/358886.358895|ref=26}}</ref> types of users (novice, casual)<ref name="klm-paper-limitations-users" /> and non-routine tasks have to be considered as well.<ref name="klm-paper-limitations-users">{{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=397, 409|doi=10.1145/358886.358895|ref=27}}</ref>

Furthermore, tasks which take more than a few minutes take several hours to model and a source of errors is forgetting operations.<ref>{{cite journal|last1=Sauro|first1=Jeff|editor1-last=Jacko|editor1-first=Julie A|title=Estimating productivity: Composite operators for keystroke level modeling|journal=Human-Computer Interaction. New Trends: Proceedings of the 13th International Conference (LNCS)|date=2009|volume=5610|page=353|doi=10.1007/978-3-642-02574-7_40|ref=28|publisher=Springer-Verlag|___location=Berlin Heidelberg}}</ref> This implies that the KLM is best suited for short tasks with few operators.

Line 157:

* [[CMN-GOMS]]

* [[CPM-GOMS]]

==References==

{{reflist|2}}

==External links==

Line 164 ⟶ 167:

*The [http://www.cs.cmu.edu/~bej/cogtool/ CogTool] project at [[Carnegie Mellon University]] has developed an open-source tool to support KLM-GOMS analysis. See also their [http://cogtool.com/publications publications] about CogTool.

*[http://www.cs.umd.edu/class/fall2002/cmsc838s/tichi/goms.html GOMS by Lorin Hochstein]

==References==

<references/>

[[Category:Human–computer interaction]]