Several factors could affect the effectiveness of product design activities. These factors can be internal to the designers like skill, knowledge and personality traits, as well as external like instructions and examples provided. Up to now, researchers and designers in the academic and industrial fields analysed the effects of at most two factors at the same time, always of the same type (internal or external). This paper describes the activities and results of the preliminary stage of a wider research that aims at understanding the relationships among heterogeneous factors (internal and external together) and at defining the best combinations of any number of them to maximize the effectiveness of product design activities. This preliminary stage aims at verifying the possibility of overcoming the limits in the number of the factors to consider as well as in their membership to the same type (internal or external). To implement this verification, some heterogeneous combinations composed by more than two factors are defined and tested. The results of the tests show that the limits can be overcome; this, in turn, allows the wider research to be carried on.
