Even better than good error messages is a careful design which prevents a problem from occurring in the first place.
- Recognition rather than recall
Make objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.
- Flexibility and efficiency of use
Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.
- Aesthetic and minimalist design
Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.
- Help users recognize, diagnose, and recover from errors
Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.
Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.
“Heuristic evaluations are easy to use, fast and as cheap as you want it” (Nielsen, 1994). In addition, as any usability problems that are found are explained with respect to recognised, it is fairly easy to produce solutions. This evaluation technique is an excellent way of finding both major and minor problems in a system. Heuristic evaluations can be made use of in the early stages of the design process. Being employed so early, problems can be found earlier, therefore making them cheaper and easier to fix than if the same problems were found later in the process, or perhaps not even at all. This gives heuristic evaluation a very good chance of being used in practical design situations.
One downside to heuristic evaluation is that, as Nielsen (1993 & 1994) states, a certain amount of expertise is required to apply the heuristics effectively. This certain skill and experience is, generally, hard to find, and expensive. Heuristic evaluations are loosely controlled and therefore run the risk of finding low priority slightly “petty” problems. Correction of these problems may not be essential.
It is expected to question how heuristic evaluation compares to other usability evaluation techniques, both empirical and inspection techniques. There have been several studies in the past which have tried to determine which of these techniques is better. Some of these investigations are described here.
Desurvire et al. (1994) compared the efficiency of empirical usability testing and heuristic evaluations in identifying infringements of usability guidelines. Laboratory analysis found 6 of the 10 guidelines were violated, whereas heuristic evaluation identified only one violation.
Jefferies et al. (1991) made a comparison between four different techniques to evaluate a software product’s user interface before it was released. The four techniques being evaluated were heuristic evaluation, software guidelines, cognitive walkthroughs, and usability testing. Their findings showed that heuristic evaluation produced the best results. Heuristic evaluation found the most usability problems of the four techniques, uncovering one-third of the most severe problems and two-thirds of the least severe. These serious problems found by several UI specialists required the least amount of effort, therefore, showing that heuristic evaluation had a distinct cost/benefit advantage.
It has often been recommended that heuristic evaluation should be used in conjunction with some kind of user testing. Ideally, a heuristic evaluation would firstly be performed to clean up the user interface, and remove any usability problems. After the system has gone back to the designers for a revamp, it would be submitted for user testing to check that the redesign had been successful, and to find any usability problems that the heuristic evaluation had missed.
In conclusion, despite some disadvantages stated above, heuristic evaluation is a valuable element of the system development process, and when implemented correctly, can produce very convincing results. However, no matter how good it may be on it’s own, a more successful end result could be achieved with a combination of heuristic evaluation and user testing.
References
Desurvive, H. (1994) ‘Chapter 7: Faster; Cheaper!! Are Usability Inspection Methods as Effective as Empirical Testing?’, in Nielsen, J. and Mack, R.L. (Eds.) Usability Inspection Methods, John Wiley and Sons, New York, pp. 173-202
Jefferies, R., Miller, J., Wharton, C., and Uyeda, K. (1991) ‘User interface evaluation in the real world: A comparison of four techniques’, in Proceedings of CHI '91, (New Orleans, LA, April 28 – May 3), ACM, New York, pp. 119-124
Nielsen, J. (1994) ‘Chapter 2: Heuristic Evaluation’, in Nielsen, J. and Mack, R.L. (Eds.) Usability Inspection Methods, John Wiley and Sons, New York, pp. 25-62
Nielsen, J. (1993) Usability Engineering, Boston: Academic Press
