This paper presents a questionnaire instrument to evaluate designs of a mobile phone and a multimedia player. The study adopted a bottom up approach by interviewing 20 participants using Kelly's Repertory Grid Technique. This resulted in two sets of 200 personal constructs participants considered relevant when evaluating a set of 15 designs for each device. Two initial questionnaire instruments were developed and their validity was examined in a survey among 156 university students. In the interview, data was also collected about participants' attitude, social norm and their intention to select a design. This data was used to develop two statistical models. These models suggest that beliefs about the preference of participants social reference group, such as peers, had a small, but significant impact on the users' selection on the more publicly noticeable mobile phone, but failed to have a significant impact on the selection of designs for the more private multimedia player.