3) Usability metrics

Background

Usability methods are often conducted to discover problems in the use of a system, preferably before it is released for use by the user. These qualitative studies often generate better insight but usability metrics are more useful to track metric goals. Unfortunately, it is more expensive to measure usability.

Usability metrics let you do two important things:

• Track progress between releases. Find out how well you are doing on a regular basis. Are you on the right track?
• Assess your competitive position. Are you better or worse than your competitors?

How to measure usability

Effectiveness

• Percent of tasks completed
• Ratio of successes to failures
• Workload
• Number of features or commands used

Efficiency

• Time to complete a task
• Time to learn
• Time spent on errors
• Percent or number of errors
• Frequency of help or documentation use
• Number of repetition or failed commands

User satisfaction

• Rating scale for usefulness of the product or service
• Rating scale for satisfaction with functions and features
• Number of times user expresses frustration or anger
• Rating scale for user versus technological control of task
• Perception that the technology supports tasks as needed by the user

Introduction to usabilty metrics

1. What is usability?
2. Usability methods
3. Usability metrics
4. Usability goals
5. Who and when to test