A comparison of the main methods for evaluating the usability of computer software : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University

The aim of this thesis is to examine the dominant computer software usability evaluation methods. Four evaluation methods (logged data, questionnaire, interview, and verbal protocol analysis) were used to evaluate three different business software types (spreadsheet, word processor, and database) using a between groups design, involving 148 individuals of both genders. When each evaluation method was examined individually, the results tended to support findings from previous research. Comparisons were made to examine the efficiency of each evaluation method, in terms of its ability to highlight usability problems (both between and within the evaluation strategy). Here support for the efficiency of the verbal protocol analysis method was found. The efficiency of using two evaluation methods was also examined, where it was found that no significant improvement was obtained over the verbal protocol analysis used by itself. A comparison addressing the practicality of using these methods was also conducted. It seems that each method has differing strengths and weaknesses depending on the stage of the evaluation. From these results a theory for the effectiveness of evaluation strategies is presented. Suggestions for improving the methods commonly used, are also made. The thesis concludes by discussing the software evaluation domain and its relationship to the wider evaluation context