Which evaluation techniques focus on evaluating a system based on established usability principles?

The evaluation techniques that focus on evaluating a system based on established usability principles are:

1. Heuristic Evaluation: This technique involves a small set of evaluators who examine the interface and judge its compliance with recognized usability principles (the "heuristics").

2. Cognitive Walkthrough: This is a usability inspection method used to identify usability issues in the user interface design. It takes the perspective of a new user to understand the system's complexity and intuitiveness.

3. Guidelines Review: This involves checking the interface against an established set of guidelines. The guidelines are usually based on usability principles.

4. Consistency Inspection: This technique checks for consistency in the design of the interface. Consistency is a fundamental usability principle.

5. Formal Usability Inspections: This involves a team of evaluators who are trained in usability. They inspect the interface for problems and violations of usability principles.

6. Pluralistic Walkthrough: In this method, users, developers, and human factors people step through a scenario, discussing each step. The focus is on understanding the users' expectations and difficulties.

7. Standards Inspection: This involves checking the interface against established standards. The standards are usually based on usability principles.

8. Style Guide Review: This involves checking the interface against a style guide. The style guide is usually based on usability principles.

These techniques are all based on the idea that there are certain universal principles of usability that should be adhered to in interface design.