1 Foundations of Usability and User Experience
Learn how usability, usefulness, and user experience differ, and how human-centered design connects user needs to measurable outcomes in context.
depends on context
describes how well specified users can achieve specified goals with a product or service in a specified . It is not simply an interface feature or another way of saying that something is easy to use.
The context includes the users, their goals and tasks, available resources, and the environment in which they work. The same product may be usable for one group or situation but not another.
Three dimensions of
has three connected dimensions: , , and . They can differ in the same experience: a person may complete a task correctly but slowly, or quickly but with frustration.
concerns how accurately and completely users achieve goals. For a booking form, success means that the correct appointment is actually booked.
concerns the resources needed to achieve goals, often measured by time, effort, or number of errors. A process can be effective but inefficient if users must repeat information across many steps.
concerns users’ responses to the experience, such as whether the process feels clear, comfortable, and acceptable. Because is subjective, it should be assessed alongside performance rather than used as a substitute for it.
Which dimension matters most depends on the task and its context. Accuracy may be especially important in clinical work, while speed may matter for a frequent routine task.
and
and address different questions. asks whether a product’s functions meet a real need; asks how well specified users can use the product to achieve goals. In practice, they work together: an easy-to-use product may not be useful if it solves the wrong problem, while valuable functions offer little benefit if people find them too difficult to use.
A transit app that clearly displays routes but omits the bus line a commuter needs is usable in some respects but not useful for that journey. An app with the correct route information may still have poor if users cannot find it or understand how to buy a ticket.
User experience extends beyond
is broader than . It includes users’ perceptions and responses arising from actual or anticipated use, such as expectations, emotions, preferences, comfort, and accomplishments. UX can be influenced by , as well as by a product’s functions and performance, its presentation, prior experience, and the circumstances of use.
therefore contributes to UX, but the terms are not interchangeable. A task can be usable while the overall experience is still disappointing.
, also called user-centered design, is an approach to developing interactive systems that focuses on users, their needs, and their requirements. It considers who will use a product, the tasks they need to perform, and the environments in which those tasks occur. Design decisions are checked against this understanding and refined as the design develops; its principles and activities apply throughout the system life cycle.
For example, a team might first learn how commuters plan trips and purchase tickets, then design a route-finding flow, and finally observe representative commuters using it. If they cannot locate the correct fare or complete a purchase, the team revises the design and evaluates it again. This connects user needs to observable outcomes rather than relying only on designers’ assumptions.
Setting goals
goals become actionable when tied to specific users, tasks, and contexts. For a transit-ticket purchase, a team could ask:
: Can a commuter select the correct route and ticket?
: How long does the purchase take, and how many steps or errors occur?
: Do users feel confident that they chose and purchased the right ticket?
These questions help teams judge whether a design works for its intended use. There is no single score that applies equally to every user and situation: measures and priorities depend on the goals and context being considered.