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GOMS Analyse

Definition

The GOMS Analyse is a specialized human information process model for observing human-computer interactions that describes a user’s cognitive structure in terms of four components. It is a widely used method by usability specialists for computer system designers because it provides quantitative and qualitative predictions about how people will use a proposed system.

Overview

The GOMS Analyse consists of methods used to achieve specific goals. These analyses are then composed of Operators at the lowest level. The Operators are specific steps that a user performs: they are assigned a specific 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 an issue to be achieved and specify a set of possible methods by which this can be achieved.
  • Operators (Operators) = elementary perceptual, motor, or cognitive actions, the performance of which is required to change some aspect of the user’s mental state or to influence the task environment.
  • Methods = describe a procedure for achieving a goal.
  • Selection Rules = are required when attempting to achieve a goal. Several methods may be available to the user to achieve this goal.
There are several GOMS variants that can be used to accurately examine and predict different aspects of an interface. For all variants, the definitions of the main concepts are the same.

The definition of all entities by the designer or analyst is flexible. For example, a Operator in one method can be a target in another method. The degree of so-called granularity is adjusted to capture what the particular evaluator is examining.

Advantages and disadvantages of GOMS Analysen

Pro
  • The GOMS approach to user modeling has strengths and weaknesses. While it is not necessarily the most accurate method for measuring human-computer interaction, it does allow visibility of all procedural knowledge. With GOMS, an analyst can easily estimate a particular interaction and compute it quickly and easily. This is only possible if the average method-time measurement data for each specific task has been previously measured experimentally with high accuracy.
Contra
  • GOMS is generally suitable for skilled users, rather than beginners or advanced users, as there is a high potential for error, which can alter the data. The model also cannot be used for learning the system or for a user using the system after a long period of non-use. Another major drawback is the failure to account for errors that even experienced users can make. Mental workload is not considered in the model, so this is an unpredictable variable. The same is true for fatigue. The GOMS Analyse is only concerned with the usability of a task on a system, not its functionality.

Software Tools

There are several tools available for creating and analyzing GOMS models. A selection is listed below:

  • QGOMS
  • CogTool (KLM-based modeling tool)
  • Cogulator Cognitive Calculator for GOMS Modeling

YouTube Video

A simple example of a GOMS Analyse for computing graphical surfaces is shown in the following YouTube video:

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Conclusion of the OM Optimiser team

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 (Goals), Operators (Operators), methods (Methods), and selection rules (Selection). The simplest and most commonly used GOMS variant is KLM-GOMS (= Keystroke-Level-Model), where empirically derived values for basic Operators such as keystrokes, key presses, double clicks and pointer movement times are used to estimate task times.

Further links

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


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