The six usability goals

Six goals, six questions you can ask of any interface

Intuition

“Is it usable?” is too vague to answer. The lecture breaks it into six goals, and each goal turns into one question you can put to a real product. The in-class case study asked you to do exactly this for the Sydney Student web application.

Lecture 1 lists the usability goals, each with a plain-language reading. The wording below is the lecture’s.

Mechanism

• Effectiveness: the product must be able to do what it is designed to do. Question: does the teapot allow you to pour tea, and refill the water?
• Efficiency: supports users in carrying out their tasks. Question: once users have learned the product, can they sustain a high level of productivity?
• Safety: protects users from dangerous conditions. Questions: what is the range of errors possible, and what measures let users recover from them easily?
• Utility: the extent to which the product provides the right kind of functionality. Question: does it provide an appropriate set of functions that lets users do all their tasks in the way they want?
• Learnability: learning the system through self-exploration. Questions: can the user work out how to use the product by exploring the interface, and how hard is it to learn the whole function set that way?
• Memorability: remembering how to use the system once learned. Question: what interface support helps users remember how to carry out tasks, especially infrequent ones?

The teapot examples are the lecture’s own: effectiveness is “can it pour and refill”, and it deliberately uses an everyday object so the question is about function, not screens.

Learnability, efficiency and memorability are three moments in a person’s use

These three are the easiest to confuse. Separate them by asking when in the person’s use the question is asked.

Compare

Learnability

First encounter. The user explores and works things out. Helped by clear navigation, familiar terminology, consistent patterns, onboarding and contextual guidance.

Efficiency and memorability

Efficiency: after learning, how fast and smoothly can they work? Helped by shortcuts, streamlined flows, low cognitive and visual load.

Memorability: after time away, can they still do it? Helped by predictable structure, familiar conventions, metaphors and icons.

Pitfall

Shortcuts and command palettes help efficiency, not learnability. Extensive embedded tutorials help a first-time user but slow a practised one, so they are a poor answer to “supports high efficiency”. Mandatory retraining is a patch over weak memorability, not a feature that creates it.

Effectiveness, safety and satisfaction round out the picture

Effectiveness is about completing the task correctly: records entered and retrieved accurately, bookings made without incorrect charges or missing information. Decoration and customisation do not demonstrate it. Safety is about errors: prevent invalid input with constraints and defaults, give feedback during critical tasks, confirm serious actions selectively, and offer undo. Hiding features is not a safety strategy because it removes utility.

Satisfaction is not one of the six goals on the Lecture 1 slide but appears in the ISO definition and in the sample questions. Responsive pages, predictable behaviour and an appealing layout raise it. Features that demand constant relearning lower it.

Optional aside

Nielsen’s five usability components are learnability, efficiency, memorability, errors and satisfaction. The lecture slide uses six goals instead: effectiveness, efficiency, safety, utility, learnability and memorability. Where the sample exam says “errors” it maps to the lecture’s safety goal, and “satisfaction” maps to the ISO definition. Follow the lecture’s list when asked to list the goals.

Goals trade off, so prioritise and measure

Lecture 1 states that all goals cannot be achieved in one design. You must understand the trade-offs, prioritise, and provide quantitative indicators to measure performance. The slide cites usability metrics from Benyon (2019, p. 256), but that figure did not extract, so the exact metric list is not available here. Lecture 3 gives two measurable examples: time for a novice to complete set tasks (learnability) and the number of functions remembered after a month away (memorability).

Try it: worked example

You are designing a ticket machine used by tourists once and by commuters daily. Name one goal to prioritise for each group and why.

Show answer and steps

AnswerTourists: learnability. Commuters: efficiency.

1. Tourists use the machine once, with no prior knowledge, so the first encounter decides success. That is learnability.
2. Commuters use it every day and already know it, so speed of repeated use matters. That is efficiency.
3. Both goals cannot be maximised together: simple guided steps help tourists but slow commuters. A design may offer a fast path for regular users alongside a guided one.
4. This is the trade-off the lecture asks you to prioritise and measure.

Recall

Name the six usability goals and say which one asks 'what happens after time away'.

Effectiveness, efficiency, safety, utility, learnability, memorability. Memorability is the one about time away.