← QCE Digital Solutions Unit 1

The five useability principles

The five checks for judging an interface: accessibility, effectiveness, safety, utility and learnability. They can conflict, so designers balance them.

Part of: QCE Digital Solutions Unit 1 — User Experiences and Interfaces — Module 7

Understanding The five useability principles in QCE Digital Solutions Unit 1

What it does: A confirmation prompt before a destructive action is a safety feature because it helps users avoid costly mistakes. A solution with the right tools for the job has good utility, while missing key tools means poor utility. The five useability principles are accessibility, effectiveness, safety, utility and learnability. Colour, font and layout are design choices, not principles. Learnability asks how quickly and easily a new user can work out how to use the interface. Effectiveness is about whether users can achieve their goal accurately. Accessibility is about whether everyone, including people with disability, can use the interface. Principles can conflict. For example, adding many confirmation pop-ups improves safety but can make a task slower and less effective, so designers must balance them.

Common mistakes: The two values passed to print() must be separated by a comma. It should be print(principle, asks). An else statement must end with a colon. It should be else: so the indented line below belongs to it.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 60–81) and word search (Modules 1–81).

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Learning
Duo
Which list shows the five useability principles?
Accessibility, effectiveness, safety, utility, learnabilityColour, font, layout, speed, price
Matches
Judging an app only on how pretty it looks and ignoring the other useability principles
↓
Useability has five principles: accessibility, effectiveness, safety, utility and learnability. Looks alone do not cover them all.
Applying
Meanings
Term
useability principles
Meaning
The five checks for judging an interface: accessibility, effectiveness, safety, utility and learnability. They can conflict, so designers balance them.
Practice
Accessibility: can everyone use it?
Testing
Gaps
← FAIL
Check Answer
Spots
2asks = "Can mistakes be undone?"
3print(principle asks)

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Quick Questions

1. Which list shows the five useability principles?
A. Accessibility, effectiveness, safety, utility, learnability ✓
B. Colour, font, layout, speed, price
The five useability principles are accessibility, effectiveness, safety, utility and learnability. Colour, font and layout are design choices, not principles.
2. A banking app asks 'Are you sure you want to send $5,000?' before it sends. Which principle does this show?
A. Safety ✓
B. Utility
Safety is about preventing mistakes and protecting users from harm, such as confirming a risky action before it happens.
3. A new student can use a school app after a short tutorial and clear labels. Which principle is this?
A. Learnability ✓
B. Effectiveness
Learnability asks how quickly and easily a new user can work out how to use the interface.
4. Which principle asks 'Can users complete their task correctly and completely?'
A. Accessibility
B. Effectiveness ✓
Effectiveness is about whether users can achieve their goal accurately. Accessibility is about whether everyone, including people with disability, can use the interface.
5. A video app has captions, adjustable text size and screen reader support. Which principle does this support?
A. Utility
B. Accessibility ✓
Accessibility means people with different abilities and needs can use the interface. Captions, resizable text and screen readers are common accessibility features.

Match the Pairs

Accessibility → Can people with different abilities, needs and devices use the interface?
Learnability → How quickly and easily can a new user work out how to use the interface?
Safety asks whether the interface protects users from mistakes and harm, such as by confirming before data is deleted. → Are you sure you want to delete this file?
Utility asks whether the interface gives users the features and tools they actually need to complete their tasks. → A photo editor with crop, resize and save tools
Judging an app only on how pretty it looks and ignoring the other useability principles → Useability has five principles: accessibility, effectiveness, safety, utility and learnability. Looks alone do not cover them all.
Adding 20 extra features for utility, which makes the screen cluttered and harder for beginners → The principles can conflict. More utility can reduce learnability, so designers must balance them.

Key Term

useability principles
The five checks for judging an interface: accessibility, effectiveness, safety, utility and learnability. They can conflict, so designers balance them.

Fill in the Blanks

1. IF altText = FALSE THEN accessibility ← FAIL
Hint: Type the principle about whether people of all abilities, such as screen reader users, can use the interface.
2. IF tasksDone = tasksSet THEN effectiveness ← PASS
Hint: Type the principle about whether users can complete their tasks accurately and completely.
3. IF deleteConfirm = FALSE THEN safety ← FAIL
Hint: Type the principle about protecting users from harm and costly mistakes, such as deleting something by accident.
4. IF hasNeededFeatures = TRUE THEN utility ← PASS
Hint: Type the principle about whether the interface provides the functions and content users actually need.
5. IF features > 20 THEN learnability ← LOWER
Hint: Type the principle that can suffer when extra features make an interface harder for new users to pick up. This shows principles can conflict.

Spot the Error

Question 1
A principle = "safety"
B asks = "Can mistakes be undone?"
C print(principle asks)
Line C — The two values passed to print() must be separated by a comma. It should be print(principle, asks).
Question 2
A effectiveness = 2
B if effectiveness >= 3:
C print("Task completed")
D else
E print("Task fails")
Line D — An else statement must end with a colon. It should be else: so the indented line below belongs to it.
Question 3
A principle = "accessibility"
B check = "Is it easy to learn?"
C print(check)
Line B — Accessibility asks whether people with different needs can use the interface. Easy to learn is the learnability principle. It should be check = "Can all users use it?".
Question 4
A principle = "learnability"
B ask = "Can users avoid harm?"
C print(principle, ask)
Line B — Learnability asks whether new users can get started easily. Avoiding harm belongs to safety. It should be ask = "Can new users start?".
Question 5
A principles = 5
B conflict = True
C if conflict = True:
D print("Balance them")
Line C — An if statement needs a condition, not an assignment. Use if conflict: (or if conflict == True:) so the code can compare, not assign.

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