ISTQB Usability Testing Glossary

About this topic

Source: ISTQB Certified Tester Usability Testing (CT-UT)

Usability testing evaluates how effectively, efficiently, and satisfyingly real people can achieve their goals with a system. These terms come from the ISTQB Usability Testing syllabus and from human-centred design practice, not from the Foundation Level syllabus.

Usability is formally defined by three measures: effectiveness (can users complete their goals accurately and completely), efficiency (at what cost in time and effort), and satisfaction (how the experience feels). A usability requirement expresses a target against one of these, which is what makes usability testable rather than merely subjective.

Evaluation methods split into two families. Formative evaluation happens during design to find problems while they are still cheap to fix. Summative evaluation happens against a finished product to measure whether it meets its targets. The think-aloud protocol, where participants narrate their reasoning while working through a usability test task, is the workhorse technique of formative evaluation.

Standardised instruments let results be compared across products and over time. The System Usability Scale and the Software Usability Measurement Inventory are questionnaires with established scoring; the Website Analysis and Measurement Inventory targets web properties specifically. Expert usability review and heuristic evaluation substitute a trained evaluator for real participants when recruiting users is impractical.

Accessibility overlaps with usability but is not the same thing. Accessibility asks whether people with disabilities can use the system at all, and is measured against standards such as the Web Content Accessibility Guidelines. A product can be accessible and still be hard to use.

What this topic covers

• Effectiveness, efficiency and satisfaction
• Formative and summative evaluation
• Think-aloud protocol
• SUS, SUMI and WAMMI
• Heuristic evaluation
• Accessibility and WCAG