Usability Principles

Accessibility definition

Usable by people with a range of abilities and disabilities

Accessibility design examples

Alt text on images, high contrast colours, keyboard navigation, large touch targets, screen-reader labels

Accessibility improvement if violated examples

Add alt text, increase contrast to at least 4.5:1, add text labels next to colour cues

Effectiveness definition

Users can achieve their goals accurately and completely.

Effectiveness design examples

Clear task flows, visible progress indicators, correct outputs, filters that narrow results

Effectiveness improvement if violated examples

Simplify the workflow, add filters, show status messages

Safety definition

Protects users from irreversible errors

Safety design examples

Confirmation dialogues (“Are you sure?”), undo, input validation, auto-save drafts

Safety improvement if violated examples

Add a confirmation step, provide an undo function, validate input before saving

Utility definition

Provides the features and functions users actually need

Utility design examples

Search, filter, sort; features matched to user goals; essential actions are present

Utility improvement if violated examples

Add the missing feature, interview users to find out what’s needed

Learnability definition

New users can learn to use the system quickly

Learnability design examples

Clear icons with labels, tooltips, onboarding tour, sensible defaults, consistent layout

Learnability improvement if violated examples

Add icons and labels, add a short onboarding, use standard patterns.

Exam answer formula

The [principle name] has been violated because [specific evidence from the scenario]. This could be improved by [a concrete design change].