Content Details - Usability engineering - Module 2 - Human Computer Interaction (HCI) - Nebula SkillHub

1. Fundamentals of Usability Engineering

Usability Engineering refers to the set of methods used to define, measure, and refine the quality of a user's experience. It aims to integrate usability goals seamlessly into the software development process.

ISO Definition of Usability (ISO 9241-11):

"The extent to which a product can be used by specified users to achieve specified goals with **effectiveness, efficiency, and satisfaction** in a specified **context of use**."

2. Measurable Usability Attributes

Usability engineering requires defining concrete, quantitative metrics (usability goals) that the design must meet.

Effectiveness

The accuracy and completeness with which users achieve specified goals.

**Metric:** Task completion rate, error rate.

Efficiency

The resources expended in relation to the accuracy and completeness achieved.

**Metric:** Time to complete task, steps taken, keystrokes/clicks required.

Satisfaction

The user's comfort and positive attitudes toward the use of the product.

**Metric:** Post-task surveys (e.g., SUS Score), qualitative feedback.

*Other key attributes often measured include **Learnability** (ease of first-time use) and **Memorability** (ease of returning after a break).*

3. Methods and Techniques

Usability engineering employs both methods that involve users and expert-based methods (without users).

A. User-Based Methods (Empirical)

Involve direct observation and testing of real users.

**Usability Testing:** Users perform benchmark tasks while being observed, measuring time and errors.
**Field Studies:** Observing users in their natural environment (Contextual Inquiry).
**Surveys/Interviews:** Gathering subjective feedback and satisfaction scores.

B. Expert-Based Methods (Analytical)

Involve specialists reviewing the interface against established guidelines.

**Heuristic Evaluation:** Experts evaluate the interface against a small set of principles (e.g., Nielsen's 10 Heuristics).
**Cognitive Walkthrough:** Simulating a user's first-time experience step-by-step to identify cognitive friction points.
**Pluralistic Walkthrough:** Bringing together users, developers, and experts to walk through the interface.

4. Nielsen's 10 Usability Heuristics

The most common set of principles used by experts in Heuristic Evaluation to assess interface quality.

**Visibility of System Status:** Users should always know what is going on (e.g., progress bars, loading indicators).
**Match Between System and the Real World:** Use familiar language, concepts, and metaphors.
**User Control and Freedom:** Provide clear "emergency exits" (undo, cancel, exit).
**Consistency and Standards:** Follow platform conventions; use the same terminology for the same concepts.
**Error Prevention:** Design systems that prevent mistakes from happening in the first place.

**Recognition Rather than Recall:** Make objects, actions, and options visible.
**Flexibility and Efficiency of Use:** Provide shortcuts for expert users while remaining intuitive for novices.
**Aesthetic and Minimalist Design:** Dialogues should not contain irrelevant or rarely needed information.
**Help Users Recognize, Diagnose, and Recover from Errors:** Error messages should be clear, polite, and constructive.
**Help and Documentation:** Provide easy-to-search documentation when necessary.

Usability engineering

Study Notes

Focus: Usability Engineering