4 Research questions
From EvolutionaryProductDevelopment
The following section summarizes the research that was undertaken in order to show that the product phases exist, if they appear in the expected order and if the product characteristics describe the product phases in the correct way. The following questions will be answered:
Do the described product characteristics appear in the order that is predicted by the product phases? Are the product phases an appropriate means to help predict the future of a product based on its history? Do products always (or most of the time) follow the product phases in the predicted sequence? Can a phasing of the life cycle of a product based on the product phases offer designers starting points for a new product development?
4.1 Research methods
Den Hertog and Van Sluijs (1995) describe the research methods that are available for research in to the effectiveness of innovations. They distinguish five groups of methods: experiment, survey, case study, action research and ethnography. For this subject, the retrospective case study and the survey are the most suitable.
4.2 Study 1 - retrospective case survey
In a retrospective case study, many aspects of one case are studied. Whereas, in a survey, a few aspects of many cases are studied. The study of one case to investigate the product phases is not enough; five seem possible. The number of aspects that have to be studied are much more limited. Therefore a comparative (multiple) retrospective case survey, a method between the survey and the case study, seems the best choice - a few cases are studied based on a small number of aspects. Study 1 therefore exists based on a retrospective survey of five cases. According to Eisenhardt (1989), between four and ten cases are usually sufficient for most surveys. In Eisenhardts paper, she advocates choosing cases that are very different from one another, leading to better insight into the applicability of the theory.
A disadvantage of a retrospective case survey is that the cases are analysed by someone that has to know the theory of product phases. If not, this person cannot judge if the studied case meets the formulated criteria. This means that there is a risk that the researcher may (unwittingly) fit the results of his research into the theory of product phases. Another disadvantage is that consulted experts have to rely on their memory.
These problems are addressed in a second study (Study 2). In this study, a method is used that was used before amongst others by Ten Klooster (2002). While developing a method to design packaging, Ten Klooster asked experts to rank steps in the design process that he had written on cards. There are several reasons why this method seems very suitable. Firstly, there is no interview, so the researcher cannot influence the results by the way he asks the questions. Secondly, the cards help the subject to memorise aspects that he would not have thought of by himself. Finally, this method allows for the use of experts (from different backgrounds) in order to rank the cards.
4.3 Study 2 - ranking by experts
This research was carried out in two parts: a pilot study and the main study. The pilot study tests to see whether the formulations of the product characteristics are clear to the subjects and if the method used (attaching stickers with statements to a field (a large piece of paper) with indications of the time the product is on the market and the market penetration of the product) is appropriate. The statements that describe product characteristics are printed on stickers. The statements are sorted by product characteristic and collected in ten folders. These folders are then offered to the subjects in random order. Within the folders the statements are also randomised. The subjects are then asked to attach the statements in a historic way, meaning that they have to position the statements in the order they expect them to take place during the course of a product's life cycle. Note, that it was possible to have statements take place simultaneously or on several separate occasions in time, and based on the experiences in the pilot study some small improvements were made.
For the main study, subjects were selected from a population of experienced industrial designers, design managers and marketing managers because it is expected that they have enough knowledge of the life cycle of products and are therefore able to work with the statements about the product characteristics.
