• Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

Chapter Four. Quantification > GOMS Keystroke-Level Model

4-2. GOMS Keystroke-Level Model

The aim of exact science is to reduce the problems of nature to the determination of quantities by operations with numbers.

James Clerk Maxwell, On Faraday's Lines of Force (1856)

I will introduce only the simplest—yet nonetheless valuable—aspect of the GOMS method: the keystroke-level model. We designers who know GOMS rarely use a detailed and formal analysis of an interface design, but that is due, in part, to our having absorbed the fundamentals of GOMS and of other quantitative methods such that our designs inherently incorporate GOMS teachings. We do bring formal analysis into play when choosing between two approaches to interface design in which small differences in speed can have significant economic or psychological effects. We can sometimes benefit from the impressive accuracy of the more complete GOMS models, such as critical-path method GOMS (CPM-GOMS) or a version called natural GOMS language (NGOMSL), which takes into account nonexpert behavior, such as learning times. We can, for example, predict how long it will take a user to execute a particular set of interface actions to within an absolute error of less than 5 percent. In these advanced models, almost all predictions fall within 1 standard deviation of the measured times (Gray, John, and Atwood 1993, p. 278). In a field in which religious wars are waged over interface designs and in which gurus often have widely varying opinions, it is advantageous to have in your armamentarium quantitative, experimentally validated, and theoretically sound techniques. For a good overview and bibliography of the various GOMS models, including her own CPM-GOMS model, see John 1995.


PREVIEW

                                                                          

Not a subscriber?

Start A Free Trial


  
  • Creative Edge
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint