Development And Validation Of A Methodology For Evaluating Product Design At The Early Stage Of Lifecycle: The Cell Phone

The objective of this dissertation is to develop a methodology for evaluating the product design in the early stage of a product development lifecycle. The methodology must involve end-users into the product design stage and provide effective usability evaluations on the product prototypes. The objectives of the research include: (1) explore critical usability factors for cell phone products and construct a framework to describe the perceived usability of those products; (2) develop and validate a methodology that incorporated with user testing and questionnaire measures to evaluate the usability of low-fidelity prototypes.To achieve the goals, the present research focuses on the cell phone product development and conducts two phases of studies. In the first phase, the underlying usability factors that essential to the perceived usability of the cell phones from the perspective of actual users were reviewed. The Perceived Usability Questionnaire (MPU) tailored to measure the perceived usability for cell phones was developed and tested through an online survey. After the exploratory factor analysis, a total of thirteen factors were derived, including: reliability, adaptability, customizability, understandability, helpfulness, learnability, frustration, navigation, recognition, consistency, simplicity, attractiveness, and controllability.In the second phase, the MPU was used as the questionnaire measure in a series task-based laboratory user testing. Before the test, a group of criteria were proposed particularly for the development of the low-fidelity paper prototypes for cell phones that can be tested in the early stage. A total of 72 collage students were recruited as participants of the experiment. The testing results from the prototypes and the actual products were compared, incorporating to the perceived complexity of the tested products.The results indicate that, the low-fidelity paper prototypes developed in the present research are proved as sensitive and effective as the actual products in the detection of usability problems. More specifically, the influences of different fidelity in prototypes and different task-based complexity level on the usability testing results of the factors that contributing to the perceived usability were determined. A group of suggestions on the usability testing with prototyping technique were proposed. The design of low-fidelity paper prototypes for the early testing of cell phones was discussed.The contribution of this research is both theoretical and practical. The thirteen-factor model is unique for the usability measurement for cell phones, including several attributes that addressing the characteristics of handset and the context of use. The criteria of low-fidelity prototyping for cell phones in the present research provide valuable recommendations to the practitioners. The usability testing results provide new evidences to the field of handset usability research. The suggestions of how to choose proper fidelity in prototyping according to the needs provide guidance to the practitioners. Most importantly, the present research proposes a feasible way to quantitatively evaluate the prototype usability with novices in the early stage of a product development lifecycle.