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Questions and Answers
What is the primary focus of the manual overrides for automatic systems?
According to the principle of NO ARBITRARY LIMITS ON USER-DEFINED NAMES, what should be ensured?
What is the primary purpose of analyzing the good and bad points of usability in an interface?
What aspect of usability is concerned with the ease of learning an interface?
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What should be included in the analysis of an interface's usability?
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What is the purpose of describing the purpose of an interface and its intended users?
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What is the main goal of user control over data in an interface?
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What is the primary benefit of including screenshots or photographs in the analysis of an interface's usability?
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What is the main objective of evaluating an interface's usability in terms of learnability, efficiency, and safety?
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What type of interfaces can be used as examples in the analysis of usability?
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Study Notes
Usability
- Usability is about creating effective user interfaces (UIs) that enable users to use the system's functionality efficiently.
- Dimensions of usability:
- Learnability (L): how easy it is for users to accomplish a task the first time they encounter the interface.
- Efficiency (E): how fast users can perform tasks once they've learned the interface.
- Safety (S): how few and recoverable errors are.
Learnability
- Learnability considers how easy it is for users to accomplish a task the first time they encounter the interface.
- Metaphors can make an interface more learnable, allowing users to make guesses about how it will work based on what they already know.
- Learning by doing: users explore the interface to achieve a goal, such as "Get rid of the redeye from my photo."
Improving Efficiency
- Make frequently-used targets big and put them near each other.
- Use screen corners and edges to reduce mouse movement.
- Avoid steering tasks or minimize steering distance.
- Use shortcuts, such as keyboard commands and menu accelerators.
- Offer recently-used or frequently-used choices.
- Use autocomplete to minimize typing.
- Implement aggregation to handle multiple items at once.
Anticipation
- A good design should put all needed information and tools within the user's easy reach.
- Anticipation can reduce the cost of switching between tasks.
Safety
- Error types:
- Slips and lapses: failure to execute a procedure correctly.
- Mistakes: using the wrong procedure for the goal.
- Capture errors: when a person starts executing one sequence of actions but veers off into another.
- Description errors: when two actions are very similar.
- Mode errors: when the same user input produces different results in different settings.
Error Prevention and Recovery
- Safety from capture errors:
- Avoid habitual action sequences with identical prefixes.
- Avoid actions with very similar descriptions.
- Keep dangerous commands away from common ones.
- Safety from mode errors:
- Eliminate modes.
- Increase visibility of mode.
- Confirmation dialogs:
- Effective ways to reduce mode errors:
- Displaying a mode indicator in the window's status bar.
- Combining different modes into one mode.
- Effective ways to reduce mode errors:
- Error messages:
- Writing error message dialogs:
- Be precise and comprehensive.
- Suggest reasons and solutions.
- Be polite and non-blaming.
- Avoid loaded words.
- Writing error message dialogs:
User Control and Freedom
- Learning by doing and dealing with errors require user control and freedom.
- Clearly marked exits:
- Long operations should be cancellable.
- All dialogs should have a cancel button.
- Wizard vs. center stage: who's in control?
- Manual overrides for automatic systems:
- Allow users to override automated systems.
- Never ask me again:
- Allow users to opt-out of repetitive prompts.
- User control over data:
- Data entered by the user should be editable by the user.
- UI should give the power to create, read, update, and delete data.
- No arbitrary limits on user-defined names:
- Allow users to define their own names and labels.
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Description
This lecture covers the importance of usability in user interface design, defining usability and its dimensions including learnability, efficiency, and safety.
