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GOMS Analysis

Definition

The GOMS analysis is a specialized human information process model for the observation of human-computer interactions, which describes the cognitive structure of a user based on four components It is a widely used method by usability specialists for computer system designers as it provides quantitative and qualitative predictions on how humans will use a proposed system.

Overview

The GOMS analysis consists of methods with which certain goals are achieved. These analyses then consist of operators at the lowest level. The operators are certain steps that a user performs: they are assigned a certain execution time.

If a goal can be achieved with more than one analysis or method, selection rules are used to determine the correct analysis:

  • Goals = symbolic structures that define a state of affairs to be achieved and a set of possible methods by which this can be achieved.
  • Operators (Operators) = elementary perceptual, motor or cognitive actions, the performance of which is necessary to change an aspect of the user’s mental state or to influence the task environment.
  • Methods = describe a procedure to achieve a goal.
  • Selection Rules = are required when trying to achieve a goal. There may be several methods available to the user to achieve this goal.
There are different GOMS variants that can be used to closely examine and predict different aspects of an interface. The definitions of the main concepts are the same for all variants.

The definition of all entities by the designer or analyst is flexible. For example, an operator in one method can be a target in another method. The level of granularity is adjusted to capture what the evaluator is investigating.

Advantages and disadvantages of GOMS analyses

Pro
  • The GOMS approach to user modelling has strengths and weaknesses. Although it is not necessarily the most accurate method for measuring human-computer interaction, it allows the visibility of all procedural knowledge. With GOMS, an analyst can easily assess a particular interaction and calculate it quickly and easily. This is only possible if the average method-time measurement data for each specific task has been measured experimentally with high accuracy beforehand.
Contra
  • GOMS is usually suitable for qualified users, less so for beginners or advanced users, as there is a high potential for errors and the data can therefore be changed. The model can also not be used for learning the system or for a user who uses the system after a longer period of non-use. Another major disadvantage is the lack of consideration of errors that even experienced users can make. The mental workload is not considered in the model, so this is an unpredictable variable. The same applies to exhaustion. The GOMS analysis only deals with the usability of a task on a system, not with its functionality.

software tools

There are various tools for the creation and analysis of GOMS models. A selection is listed below:

  • QGOMS
  • CogTool (KLM-based modeling tool)
  • Cogulator Cognitive computer for GOMS modelling

YouTube video

The following YouTube video shows a simple example of a GOMS analysis for calculating graphical user interfaces:

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Conclusion of the OM Optimiser Team

[su_quote]GOMS is a family of human performance prediction models that can improve the efficiency of human-computer interaction by identifying and eliminating unnecessary user actions. GOMS stands for Goals, Operators, Methods and Selection. The simplest and most commonly used GOMS variant is KLM-GOMS (= Keystroke Level Model), which uses empirically derived values for basic operators such as keystrokes, key presses, double clicks, and pointer movement times to estimate task times.
[/su_quote]

Further links

http://www.medien.ifi.lmu.de/
https://www.usability-in-germany.de/


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