Keystroke-level model: Difference between revisions

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{{Short description|Form of human–computer interaction}}

In [[human&ndash;computer interaction]], the '''keystroke-level model''' ('''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|s2cid=5918086|ref=1|doi-access=free}}</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=978-0898592436|pages=ix–x|ref=4|url=https://archive.org/details/psychologyofhuma00stua}}</ref> The keystroke-level model is still relevant today, which is shown by the recent research about mobile phones and touchscreens (see [[#Adaptions|Adaptions]]).

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* '''R''' (response time of the system): the response time depends on the system, the command and the context of the command. It is only used when the user actually has to wait for the system. For instance, when the user mentally prepares (M) for executing their 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|archive-date=19 March 2015|archive-url=https://web.archive.org/web/20150319195627/http://www-personal.umich.edu/~itm/688/KierasKLMTutorial2001.pdf|url-status=dead}}</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 book|last1=Sauro|first1=Jeff|title=Human-Computer Interaction. New Trends|editor1-last=Jacko|editor1-first=Julie A|chapter=Estimating productivityProductivity: Composite operatorsOperators for keystrokeKeystroke levelLevel Modeling modeling|journaltitle=Human-Computer Interaction. New Trends:|editor1-last=Jacko|editor1-first=Julie Proceedings of the 13th International Conference (LNCS)A|date=2009|volume=5610|page=355|doi=10.1007/978-3-642-02574-7_40|ref=10|publisher=Springer-Verlag|___location=Berlin Heidelberg|series=Lecture Notes in Computer Science|isbn=978-3-642-02573-0}}</ref>

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

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| colspan="2" | suggested operators

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| B (mouse button press or release) || 0.1<ref>{{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=2|archive-date=19 March 2015|archive-url=https://web.archive.org/web/20150319195627/http://www-personal.umich.edu/~itm/688/KierasKLMTutorial2001.pdf|url-status=dead}}</ref>

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| Click a Link/ Button || 3.73<ref name="sauro-suggested-operators">{{cite book|last1=Sauro|first1=Jeff|chapter=Estimating Productivity: Composite Operators for Keystroke Level Modeling |title=Human-Computer Interaction. New Trends|editor1-last=Jacko|editor1-first=Julie A|chapter=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=357|doi=10.1007/978-3-642-02574-7_40|ref=10|publisher=Springer-Verlag|___location=Berlin Heidelberg|series=Lecture Notes in Computer Science|isbn=978-3-642-02573-0}}</ref>

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| Pull-Down List (No Page Load) || 3.04<ref name="sauro-suggested-operators" />

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== Advantages ==

The KLM was designed to be a quick and easy to use system design tool, which means that no deep knowledge about [[psychology]] is required for its usage.<ref name="klm-paper-advantages">{{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|s2cid=5918086|ref=19|doi-access=free}}</ref> Also, task times can be predicted (given the [[#Limitations|limitations]]) without having to build a [[prototype]], recruit and test users, which saves time and money.<ref>{{cite book|last1=Sauro|first1=Jeff|chapter=Estimating Productivity: Composite Operators for Keystroke Level Modeling |title=Human-Computer Interaction. New Trends|editor1-last=Jacko|editor1-first=Julie A|chapter=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|pages=352–361|doi=10.1007/978-3-642-02574-7_40|ref=20|publisher=Springer-Verlag|___location=Berlin Heidelberg|series=Lecture Notes in Computer Science|isbn=978-3-642-02573-0}}</ref> See the [[#Example|example]] for a practical use of the KLM as a system design tool.

== Limitations ==

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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|s2cid=5918086|ref=26|doi-access=free}}</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"/>

Furthermore, tasks which take more than a few minutes take several hours to model and a source of errors is forgetting operations.<ref>{{cite book|last1=Sauro|first1=Jeff|chapter=Estimating Productivity: Composite Operators for Keystroke Level Modeling |title=Human-Computer Interaction. New Trends|editor1-last=Jacko|editor1-first=Julie A|chapter=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|series=Lecture Notes in Computer Science|isbn=978-3-642-02573-0}}</ref> This implies that the KLM is best suited for short tasks with few operators.

In addition, the KLM can not make a perfect prediction and has a root-mean-square error of 21%.<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=978-0898592436|pages=[https://archive.org/details/psychologyofhuma00stua/page/275 275]|ref=29|url=https://archive.org/details/psychologyofhuma00stua/page/275}}</ref>

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{| class="wikitable"

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! Design A: drag the file into the trash can<ref>{{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=31|page=3|archive-date=19 March 2015|archive-url=https://web.archive.org/web/20150319195627/http://www-personal.umich.edu/~itm/688/KierasKLMTutorial2001.pdf|url-status=dead}}</ref> !! Design B: use the short cut “control + T”<ref>{{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=31|page=6|archive-date=19 March 2015|archive-url=https://web.archive.org/web/20150319195627/http://www-personal.umich.edu/~itm/688/KierasKLMTutorial2001.pdf|url-status=dead}}</ref>

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| method encoding (operator sequence)<ref>{{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=32|page=9|archive-date=19 March 2015|archive-url=https://web.archive.org/web/20150319195627/http://www-personal.umich.edu/~itm/688/KierasKLMTutorial2001.pdf|url-status=dead}}</ref>|| method encoding (operator sequence)<ref>{{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=33|page=10|archive-date=19 March 2015|archive-url=https://web.archive.org/web/20150319195627/http://www-personal.umich.edu/~itm/688/KierasKLMTutorial2001.pdf|url-status=dead}}</ref>

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