Usability, user experience, utility and usefulness

Usability is judged against a user, a goal and a context

Intuition

A teapot can be wonderful for one person and useless for another. Whether it works depends on who is pouring, what they want, and where they are. Usability is that idea made precise.

Lecture 1 gives the definition of usability: the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use. Three words are marked “specified”. Change the user group, the goal or the setting and the usability changes, even if the product does not.

The three outcome measures are effectiveness, efficiency and satisfaction. The lecture’s list of usability goals (next topic) expands these into six design-facing goals.

User experience is the person’s perceptions and responses

User experience is the quality of experience a person has when interacting with a specific design. The lecture quotes ISO 9241-210: user experience is “a person’s perceptions and responses that result from the use of a product, system or service”. It is about how the interaction felt to the person, not only whether the task was finished.

Compare

Usability

Can specified users reach specified goals effectively, efficiently and with satisfaction in a specified context?

Defined through outcomes against goals.

User experience

What did the person perceive and feel before, during and after use?

ISO 9241-210: perceptions and responses resulting from use of a product, system or service.

Utility is the function, usefulness needs function and ease together

The lecture defines utility as the extent to which a product provides the right kind of functionality, so users can carry out all their tasks in the way they want. It is listed as a usability goal on the slide, but the exam prep treats it as a separate axis from usability.

Usefulness is not defined on the Lecture 1 slides. The sample exam questions (8 to 10) fix how it is used: usefulness requires both sufficient usability and sufficient utility. That gives four combinations.

Usability	Utility	What you have
High	High	A useful product
High	Low	Easy to use but not useful: it lacks the features users need
Low	High	Powerful but hard to use. Potentially useful if usability improves
Low	Low	Neither

Exam detail

Exam prep answers to remember. A product can be usable but not useful if it lacks utility (true). High utility does not guarantee a good user experience (so that option is false). Usefulness needs both usability and utility (true). Usability is not “more important” than utility for usefulness (false). Usefulness is not “solely” determined by ease of use (false). A hard-to-use but powerful tool is high in utility, low in usability, and potentially useful if usability improves.

Pitfall

Words like “always”, “solely” and “only” signal a wrong option in this topic. Utility and usability each contribute and neither alone guarantees usefulness. Also keep usability apart from aesthetics: a good-looking interface can still be unusable.

Optional aside

The slides use the phrase “user experience goals” but the figure that lists them did not survive text extraction. The textbook (Sharp, Preece and Rogers) lists desirable ones such as satisfying, enjoyable and motivating, and undesirable ones such as frustrating and annoying. Treat that as background only, since the lecture figure could not be read here.

Recall

State the usability definition and the three words it marks as 'specified'.

Usability is the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use. The three specified items are users, goals and context of use.