USABILITY ASSIGNMENT

Usability Assignment

Usability Assignment

Introduction

This report presents a prototype interface for an interactive application codenamed Blue Whale that addresses the problems encountered in the following scenario through the use of PACT analysis, observation and research.

Stage 1

Heuristic evaluation is a good method for finding both major and minor problems in a user interface. As one might have expected, major problems are slightly easier to find than minor problems, with the probability for finding a given major usability problem at 42 percent on the average for single evaluators in six case studies (Nielsen 1992, 315-320). The corresponding probability for finding a given minor problem was only 32 percent.

Even though major problems are easier to find, this does not mean that the evaluators concentrate exclusively on the major problems. In case studies of six user interfaces (Nielsen 1992, 315-320), heuristic evaluation identified a total of 59 major usability problems and 152 minor usability problems. Thus, it is apparent that the lists of usability problems found by heuristic evaluation will tend to be dominated by minor problems, which is one reason severity ratings form a useful supplement to the method.

Even though major usability problems are by definition the most important ones to find and to fix, minor usability problems are still relevant. Many such minor problems seem to be easier to find by heuristic evaluation than by other methods. One example of such a minor problem found by heuristic evaluation was the use of inconsistent typography in two parts of a user interface. The same information would sometimes be shown in a serif font (like this one) and sometimes in a sans serif font (like this one), thus slowing users down a little bit as they have to expend additional effort on matching the two pieces of information. This type of minor usability problem could not be observed in a user test unless an extremely careful analysis were performed on the basis of a large number of videotaped or logged interactions, since the slowdown is very small and would not stop users from completing their tasks.

Usability problems can be located in a dialogue in four different ways: at a single location in the interface, at two or more locations that have to be compared to find the problem, as a problem with the overall structure of the interface, and finally as something that ought to be included in the interface but is currently missing. An analysis of 211 usability problems (Nielsen 1992, 315-320) found that the difference between the four location categories was small and not statistically significant. In other words, evaluators were approximately equally good at finding all four kinds of usability problems. However, the interaction effect between location category and interface implementation was significant and had a very large effect.

Alternating Heuristic Evaluation and User Testing

Even though heuristic evaluation finds many usability problems that are not found by user testing, it is also the case that it may miss some problems that can be found by user ...