Methodology/Approach: The authors conducted usability experiments in both the planning and preproduction phases of the new Sanyo AWD-AQ3000 prototype; comparing it to the conventional model. The subjects were asked to set the machine to perform the designated washing tasks using the two simulator and preproduction panels. The time and the sequence of steps to complete each task were recorded along with a subjective 5-point irritation score for each subject. All operations were recorded on video tape. The hierarchical task analysis was used to determine the incorrect steps. The new model using the improvements based on the results was released in February 2008.
Findings: Based on the results of the analysis at the planning phase; we decided to use the control knob to alleviate the operational steps and irritation score; and isolate the mode-selection buttons from the others. The locations of the start button and the control knob were also changed. The rotation of the control knob was consistently related with curved arrows pointed both ways on the horizontal display of LCD. Based on the results at the preproduction phase; in particular; changing the layout and adding the control knob was found to improve the results for the waterless function (disinfects and deodorizes using ozone instead of water) task; the average completion time of which was 34.5% that of the conventional model. Small problems noted in the experimental stage were fixed on the final production model.
Originality/Value of paper: The practical case example of usability improvement for the commercial product development; from the planning phase to the release was described.
Keywords: Usability; Automatic washing-drying machine; Hierarchical task analysis; Quantitative analysis