What is Usability?
What is usability? Usability focuses on how easily people can finish a particular task. Under ISO 9241-11 standard, it is defined as “the effectiveness, efficiency, and satisfaction with which specified users achieve specified goals in particular environments.
Below are the three constructs of usability with their definitions:
- Effectiveness: the accuracy and completeness with which specified users can achieve specified goals in particular environments.
- Efficiency: the resources expended in relation to the accuracy and completeness of goals achieved.
- Satisfaction: the comfort and acceptability of the work system to its users and other people affected by its use.
How is it different from UX?
The term User Experience (UX) is a more recently coined term. People tend to use UX interchangeably with “usability” that predates it.
The ISO 9241-210 standard defines User Experience (UX) as a person’s perceptions and responses that result from the use or anticipated use of a product, system or service. On top of this, it considers user experience to include the following attributes of users:
- Physical and psychological responses
- Behaviors and
Three factors, namely system, user, and context of use influence user experience.
The goals of UX and usability are similar in a way that they promote the creation of interfaces to delight users. However, the subtle difference between the two is that UX focuses on understanding the feelings of users, while usability focuses on observing and learning specific user behavior and patterns.
What does usability in usability testing measure?
Typically, usability testing measures the three constructs of usability, namely effectiveness, efficiency, and satisfaction.
The metrics used to measure usability include:
- Task success rate
- Time taken to complete a task
- System Usability Scale (SUS)
- Post-Study System Usability Questionnaire (PSSUQ)
- Net Promoter Score
However, products and services may vary across industry and technology is rapidly evolving. As such, it is very much up to you to decide the best metrics to adopt to measure the three defined constructs.