Model-Based Evaluations

Get introduced to the GOMS and KLM model used in model-based evaluations.


Another expert-based evaluation technique is the model-based evaluation. This approach uses cognitive and design models. These models help to identify project specifications along with design evaluation. In this lesson, we are going to study two models: the GOMS model and the Keystroke-level model.

The GOMS model

GOMS stands for Goals, Operations, Methods, and Selection.

  • Goals: This describes user goals, i.e. what the user wants to achieve. For example, “Close a tab in Safari,” is a goal.

  • Operations: The set of basic actions that users can perform to interact with the system and achieve a goal. For example, “press key X,” and “mouse click,” are operations.

  • Methods: These are the different ways of achieving the same goal. Method X will have a different set of subgoals from method Y. Both methods can be used to achieve the goal. For example, a tab in Safari can be closed either by selecting the “close tab” option from the menu, by clicking the “cross icon” on the tab, or by using the key shortcut “command+W”. There are three methods to achieve this goal.

  • Selection: These are the conditions and situations that predict which method will be used. Selection basically depends on three things:

    • Particular users
    • System state
    • Goal details

    For example, an expert user will prefer either the “cross icon” method or the “command+W” shortcut. In contrast, a novice user may not know about the shortcut and chooses to close the tab using the menu option or clicking the “cross icon.”

GOMS example

Here is an example of a task to move the word “cute” before the word “baby” in the following sentence.

“What a baby she is cute!”

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