Understanding HCI

Heuristic Evaluation

What is a Heuristic Evaluation?

The word 'heuristic' means expert. So a 'Heuristic Evaluation' of a system is an 'Expert Evaluation'. This expert evaluator uses a checklist of heuristics against which the system (website, multimedia CD ROM, windows application, washing machine) is graded.

Why Use it?

It allows the designer of a system or interface to get feedback from other experts in the field.

Participants Needed

Experts

4 or 5 experts needed

Who can be an expert ?

The designer of the system

The designer of a system cannot be the expert evaluator, because they cannot see their own built in assumptions. For example, as I am writing this page I understand what I am trying to explain, but I can only be fairly certain that the readers also understand, if someone else (who knows nothing about the subject) can also understand it. Because the designer is a type of expert, they may not see problems that novice users might have with the system. The designer is also unlikely to be visually, motor or cognitively impaired and it can be impossible to then to comprehend what the system might look like from these perspectives. So the system designer cannot be the systems 'Heuristic Evaluator'.

Another designer

However, a system designer may be a Heuristic Evaluator of a system another designer has created, as they will likely see at least some of the mistakes the other designer has made. This in fact is the most usual scenario. To increase the likelihood of detecting all possible interface errors, several independent evaluators may be used. According to Jacob Nielson, the recommended number is 5. After 5, the time and cost out way the benefits of finding further errors.

A person who knows a lot about the system

A person who knows a lot about the system can also function as an expert evaluator, as they will have an expert understanding of task flows and expected system outcomes that a designer may not fully understand. These experts can catch errors and mistakes of a nature that a designer might never see.

A person who will use the system

A person who will use the system is not usually considered an expert in the system. For this reason they are not generally used for Heuristic Evaluation, although users are commonly involved with other evaluation methods such as User Testing and Task Analysis.

More than one of the above

Occasionally a person is available who is both a designer and an expert of the system being created. This person is the most likely to find the most errors and therefore are the most valuable team member during the evaluation phases.

Task List

As mentioned above, a checklist is required against which to grade the system being evaluated. The list below consists of 9 checks, though others have 10 or 11.

  1. Familiarity, Consistency and Clarity of Elements
  2. Appropriate Language
  3. Natural and Logical Ordering of Information
  4. User Control and Freedom
  5. Navigational Support
  6. Recognition Rather than Recall
  7. Timely Feedback, Error Prevention and Recovery and Efficiency
  8. Meets User Requirements
  9. Aesthetics

Conditions required

Elements should be listed along with:

  1. the appropriate screen(s) / element
  2. the heuristic guideline(s) it does not comply with
  3. a description of the particular error identified
  4. a description of the user difficulty presented
  5. a suggested solution
  6. the severity of the problem - severity should be rated from 1 to 5, 5 being the most severe

The list should be ordered in descending order of severity, from most severe to least, and then by screen.

Examples

  1. Screen shots & Scenario for Heuristic evaluation of College PDA

Limitations Of method

Experts can pick up many obvious errors...
.. but ultimately the system MUST be tested with real, representative people

Exercise

Using the screen shots and scenario given, and the Heuristic Evaluation Sheet (.doc) / Heuristic Evaluation Sheet (.rtf), complete a heuristic evaluation of PDA screen designs for a Gastro-Intestinal unit

Reading