EN
The purpose of this study was to set up a method to assess the usability of everyday products. It was examined to compare the usability of three insulin self-injection devices (Pen 1, Pen 2 and Dial) in young and older adults. The experiment set out to determine the relationship among error, subjective eva¬luation and operation time, and how the user makes errors in using these devices. It was conducted for 99 people (51 young adults and 48 older adults) who have never come into contact with these devices. By the factor analysis, it was found that subjective evaluation was composed of five factors. The analysis of type of error clarified the difference of usability between young and older people. In addition, each self-injection device was characterized by the relationships among contents of error, operation time, and subjective eva¬luation. It was suggested, at large, that usability of Pen 1 was lower than the other two devices, and young adults did not take more time to operate these devices than older adults, but they shortened operation time. It was suggested that the technique of measurement and evaluation of usability employed in this study would enable us to comprehend various aspects of usability.