← QCE Digital Solutions Unit 3

The six useability principles

Six criteria for judging an interface: accessibility, effectiveness, efficiency, error tolerance, engagement and ease of learning. Each feature of a design can be matched to one of them.

Part of: QCE Digital Solutions Unit 3 — Interactions Between Users, Data and Digital Systems — Module 131

Understanding The six useability principles in QCE Digital Solutions Unit 3

What it does: A one-tap shortcut cuts the number of steps needed to finish a task, which is the useability principle of efficiency. Features that let people with different abilities and needs use the interface support accessibility. Confirmation prompts help users avoid or recover from mistakes, which is error tolerance. Rewards, challenges and appealing design make an interface enjoyable and keep users interested, which is engagement. Effectiveness is about whether users can achieve their goals completely and correctly, no matter how fast or fun it is. Rewards and streaks aim to hold the user's interest, so the correct principle is engagement.

Common mistakes: Alt text lets screen reader users understand images, so it supports accessibility, not efficiency. Line 2 should be 'Alt text -> accessibility'. Efficiency is about completing a task with minimal time and effort. Fewer taps make the task more efficient, so the line should say 'more efficient'.

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Learning
Duo
Which list correctly names the six useability principles?
Accessibility, alignment, contrast, balance, space, text formattingAccessibility, effectiveness, efficiency, error tolerance, engagement, ease of learning
Matches
Feature: progress badges and streak rewards. Principle: Effectiveness
↓
Badges and rewards keep users interested and motivated, so they match engagement, not effectiveness. Effectiveness is whether users can complete tasks accurately and completely.
Applying
Meanings
Term
useability principles
Meaning
Six criteria for judging an interface: accessibility, effectiveness, efficiency, error tolerance, engagement and ease of learning. Each feature of a design can be matched to one of them.
Practice
Alt text on images -> accessibility
Testing
Gaps
principle:
Check Answer
Spots
1App review: canteen app
2Alt text -> efficiency

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Quick Questions

1. Which list correctly names the six useability principles?
A. Accessibility, effectiveness, efficiency, error tolerance, engagement, ease of learning ✓
B. Accessibility, alignment, contrast, balance, space, text formatting
The six useability principles are accessibility, effectiveness, efficiency, error tolerance, engagement and ease of learning. Alignment, contrast, balance and space are UI design principles, which are a different set.
2. A school app offers a text-to-speech option for students with low vision. Which principle does this feature support?
A. Accessibility ✓
B. Engagement
Features that let people with different abilities and needs use the interface support accessibility.
3. A banking app asks 'Are you sure you want to send $5000?' before confirming a transfer. Which principle is this?
A. Efficiency
B. Error tolerance ✓
Confirmation prompts help users avoid or recover from mistakes, which is error tolerance.
4. A new student opens a timetable app and a short guided tour shows them where everything is. Which principle is this?
A. Effectiveness
B. Ease of learning ✓
Tutorials and onboarding help new users learn to use the interface quickly, which is ease of learning.
5. A food delivery app lets you reorder your usual meal in two taps. Which principle does this feature best show?
A. Efficiency ✓
B. Accessibility
Efficiency is about completing a task with minimal time and effort, such as fewer taps or steps.

Match the Pairs

Accessibility → Whether people with a wide range of abilities and needs can use the interface, for example through screen reader support or adjustable text size
Error tolerance → How well the interface prevents mistakes and helps users recover from them, for example with an undo button or a confirmation prompt
A feature that lets users finish a common task in fewer steps, saving time and effort (efficiency) → One-tap reorder button on the home screen
A feature that helps new users learn the interface quickly without a manual (ease of learning) → Short guided tutorial shown on first login
Feature: progress badges and streak rewards. Principle: Effectiveness → Badges and rewards keep users interested and motivated, so they match engagement, not effectiveness. Effectiveness is whether users can complete tasks accurately and completely.
Feature: an undo button after deleting a file. Principle: Ease of learning → Undo lets users recover from a slip, so it matches error tolerance. Ease of learning is about how quickly new users pick up the interface.

Key Term

useability principles
Six criteria for judging an interface: accessibility, effectiveness, efficiency, error tolerance, engagement and ease of learning. Each feature of a design can be matched to one of them.

Fill in the Blanks

1. feature: alt text on images principle: accessibility
Hint: Type the principle about letting people with different abilities use the interface.
2. feature: search returns the right result principle: effectiveness
Hint: Type the principle about whether users can complete a task correctly and fully.
3. feature: one-tap checkout, fewer steps principle: efficiency
Hint: Type the principle about completing tasks with the least time and effort.
4. feature: confirm box before deleting principle: error tolerance
Hint: Type the principle about preventing mistakes and helping users recover from them.
5. feature: tutorial for first-time users principle: ease of learning
Hint: Type the principle about how quickly a new user can work out how to use the interface.

Spot the Error

Question 1
A App review: canteen app
B Alt text -> efficiency
C Undo -> error tolerance
Line B — Alt text lets screen reader users understand images, so it supports accessibility, not efficiency. Line 2 should be 'Alt text -> accessibility'.
Question 2
A Principle: efficiency
B Task: pay for lunch
C Old way: 6 taps, new: 2
D Fewer taps = less efficient
Line D — Efficiency is about completing a task with minimal time and effort. Fewer taps make the task more efficient, so the line should say 'more efficient'.
Question 3
A Principle: effectiveness
B Task: book a tutor
C Booking fails = effective
Line C — Effectiveness means the user can complete the task correctly. A booking that fails is not effective. It should read 'Booking works = effective'.
Question 4
A Feature: onboarding tour
B Principle: error tolerance
C New users start quickly
Line B — An onboarding tour helps new users learn the interface, so it matches ease of learning. Error tolerance is about recovering from mistakes.
Question 5
A Feature: animated game badges
B Principle: error tolerance
C Users can recover from slips
Line A — Error tolerance needs a feature that prevents or recovers from mistakes, like a delete confirmation. Animated badges relate to engagement, so line 1 should be 'Feature: confirm on delete'.

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