06 Safety

Summary

This session discusses the third dimension of usability, 'safety,' focusing on human error, error prevention, and error messages. It explains different types of human errors, such as slips, lapses, and mistakes, categorizing them based on skill-based, rule-based, and knowledge-based behaviors. Examples of common errors in user interfaces, such as capture, description, and mode errors, are provided. The session also covers strategies to reduce errors, such as improving design, using confirmation dialogs, and offering clear, helpful error messages to enhance the user experience and system safety.

Takeaways

• 😀 Safety is the third dimension of usability, focusing on error prevention and handling, following previous discussions on efficiency and learnability.
• 🛑 Human error is categorized into two types: slips (execution failures) and mistakes (rule-based or knowledge-based errors).
• 🔄 Slips occur during routine tasks, where a user knows the correct procedure but performs it incorrectly due to execution failure.
• 💡 Mistakes happen when users apply the wrong procedure to achieve a goal, often in unfamiliar situations where problem-solving is required.
• 🧠 Errors can be classified into skill-based, rule-based, and knowledge-based behaviors, each affecting how users perform tasks.
• 🛠 Skill-based errors, such as slips, often occur in routine tasks, while rule-based and knowledge-based errors involve applying incorrect procedures.
• 📋 Slips can be further broken down into specific types, including capture errors, description errors, and mode errors.
• 🔔 Effective error prevention strategies include avoiding similar action sequences, separating dangerous commands, and offering clear confirmation dialogs.
• ✍️ Error messages should be simple, clear, and avoid technical jargon, helping users understand the issue and suggesting solutions.
• 🚫 Error messages should avoid blaming the user and instead focus on system limitations or providing constructive feedback.

Q & A

What is the third dimension of usability discussed in the session?

The third dimension of usability discussed is safety, often referred to as error prevention.

What are the two types of errors mentioned in the script?

The two types of errors mentioned are 'slips and lapses' and 'mistakes'.

What is the main difference between a slip and a mistake?

A slip is the failure to execute a known procedure correctly, while a mistake is the use of an incorrect procedure to achieve a goal.

How are slips and lapses categorized in relation to cognitive behavior?

Slips and lapses are categorized as skill-based errors, typically occurring during routine tasks.

What causes a slip error in user interaction?

A slip error is caused by failure in execution, such as incorrect observation or an unintended action while following a familiar routine.

How is a mistake classified in terms of knowledge and rules?

A mistake occurs when a user applies the wrong rule or knowledge-based action in a given situation, often without realizing the error.

Can you give an example of a mistake in a user interface context?

An example of a mistake in a user interface is sending a large photo via email without realizing the file size exceeds email capacity limits.

What is a 'capture error' as discussed in the script?

A capture error happens when a user begins an action but unintentionally switches to a more familiar sequence, such as walking to a familiar destination instead of the intended one.

What is the significance of confirmation dialogs in error prevention?

Confirmation dialogs help prevent irreversible actions by requiring users to confirm their intentions before proceeding, thus reducing the likelihood of errors.

What is one recommendation for reducing 'mode errors'?

One recommendation for reducing mode errors is to create clear indicators when a mode, such as Caps Lock, is active, so users are aware of the current mode.