Interface efficiency helps quantify whether a design is functional or not. It is a fantastic technique to design better interfaces. It also tells us when you can stop looking for better design. Efficiency is usually measured as time on task, one of the quintessential usability metrics. It does not tell us how easy the interface is. It does not help us determine how fast the user will be and it certainly cannot detect beauty.
Can a new design make things faster? Sometimes. But by the time usability is measured it’s too late to change the interface!
Interface efficiency helps us determine when is the right time to stop looking for a new design.
KLM: The KLM requires that you describe how the user would do the task in terms of actions at this keystroke level. Basically, you list the sequence of keystroke-level actions the user must perform to accomplish a task, and then add up the times required by the actions. KLM helps us determine the time taken for various key stroke level tasks.
A few key stroke level tasks can sum up everything we do with a computer within the metrics of time:
- Homing: Moving Hand to Keyboard or Mouse: 360ms
- Clicking: the Mouse: 230 ms
- Pointing: with the Mouse: 1100ms
- Mental Operations: (Deciding what to Do): 1350 ms
GOMS is a modelling technique for Human Computer Interaction is based on the CMN model. It is a design method based on cognitive psychology. It takes into account 4 levels of cognitive activities:
- Goals: What the system user wants to accomplish
- Operators: Are actions available to user. Can by physical or mental.
- Methods: What methods can the system user use to accomplish his/her goals
- Selection Rules: What methods will the system user select to accomplish his goals.
Understanding Interface Efficiency through Aza’s blog was very interesting. However, KLM and GOMS took me a lot of time to understand. I understood the concepts thoroughly and its applications, however I must revise this again after a few weeks as many new terms were introduced in this lesson and this was possibly one of the most intensive one so far!
I have started playing around with CogTools. So far, I do not understand much. Will need to read their documentations.