Usability Goals
On this page 9 headings
05. Five usability goals
Usability (ISO 9241-11): 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.
| Usability goal | Meaning |
|---|---|
| Effectiveness | How good a system is at doing what it is supposed to do — is it capable of allowing people to learn well, carry out their work efficiently, access the information they need, buy the goods they want? |
| Efficiency | The way a system supports users in carrying out their tasks — common tasks through a minimal number of steps; once learned, users can sustain a high level of productivity. |
| Safety | Protect users from dangerous conditions and undesirable situations; help users avoid unwanted actions accidentally and provide recovery from errors. |
| Learnability | How easy a system is to learn to use. |
| Memorability | How easy a system is to remember how to use, once learned — especially important for systems used infrequently; users shouldn’t have to relearn tasks after months away. |
06. Effectiveness: doing the intended task
How good a system is at doing what it is supposed to do — is it capable of allowing people to learn well, carry out their work efficiently, access the information they need, buy the goods they want?
EXAMPLE Google — minimal design with the main functionality (search) at the centre; Amazon — all necessary information (cost, delivery date, offers) on a single page, no need to scroll.
07. Efficiency: reducing unnecessary effort
The way a system supports users in carrying out their tasks — common tasks through a minimal number of steps; once learned, users can sustain a high level of productivity.
EXAMPLE Buying on Amazon — Buy Now → select delivery address → select payment method → buy; Amazon saves the delivery address and card details so returning users can buy quickly.
08. Safety in safety-critical systems
Two aspects of safety. First: protecting the user from dangerous conditions and undesirable situations — e.g. user interfaces of X-ray machines and chemical plants. Therac-25 was a radiation therapy machine, first of its kind, with a dual treatment mode, using software-based safety systems rather than hardware controls. One day the operator pressed X (X-ray mode) instead of E (electron mode); this led to excess radiation and the death of a patient.
09. Safety: avoid accidental actions
THINK Recall software applications that you have used. How have they reduced the risk of wrong keys being pressed or provided a means of recovery after errors? Pause and write down your responses before reading further.
Second: helping users in any situation avoid carrying out unwanted actions accidentally — reduce the risk of wrong keys being pressed. Example: in document software the Save and Close buttons are far apart.
10. Safety: recovering from mistakes
Provide a means of recovery if users make errors: accidentally deleted a file → recover from trash; computer shut down while editing in Word → recovery options next time; Undo (Ctrl+Z); WhatsApp — delete a message sent by mistake.
11. Learnability for new users
How easy a system is to learn to use. People want to get started right away without much effort — e.g. Facebook, Instagram, WhatsApp, Amazon are learned without reading a manual.
12. Learning more complex tasks
THINK What are ways in which you can help users learn how to use a complex system? Pause and write down your responses before reading further.
For complex systems: Wizards — a step-by-step process that breaks a complex task into simpler tasks. Tours — highlight important areas or features of a page with lots of information, for new learners. Templates — provide defaults or structure for a specific type of task (e.g. a resume template), so you don't start from scratch.
13. Memorability versus user experience
How easy a system is to remember how to use, once learned — especially important for systems used infrequently; users shouldn’t have to relearn tasks after months away. Example: Microsoft Word — meaningful icons, command names and menu options help users remember where to find a tool.
Beyond usability, we want users to experience positive emotions — satisfying, enjoyable, fun, helpful, entertaining, motivating, emotionally fulfilling. These goals are more subjective and concern how users experience the product from their perspective.
Important distinction: memorability is a usability goal, while enjoyable or satisfying use belongs to user-experience goals.