3.2 Multiple Case Study Approach 45
45
to participate immediately. Nine of the selected cases were willing to participate
in the study.
3.2.1.3 Design instruments
The next step is preparing the data collection instruments. In this regard, the
previously mentioned quality criterion data triangulation becomes important.
Combining multiple data collection methods such as interviews, observations and
archival sources is recommended to achieve a stronger substantiation of results
(Eisenhardt 1989). In this case study, secondary data/ documents which have been
publicly published by the corporation, case interviews with one representative
from each case, and case notes taken during or after each interview were used as
sources of data.
Semi-structured expert interviews with open-ended questions have been con-ducted. Prior to this, interview guidelines were created so that the interviews were
structured and to ensure the inclusion of specific topic areas (the interview guideline
can be found in the Appendix 8.1). To test the relevance and comprehensibility of
the open-ended questions, extracts of the interview guideline have been tested in
short preliminary interviews conducted with five test cases via phone between
May and July 2014.
Questions were asked in such a way as to encourage the interviewee to narratefreely and also to allow a certain degree of flexibility to the conversation (Wrona
2005). The advantage of this kind of interview is that it gives deep insights. The
interview guidelines provided structure to the interviews making the cases easier
to compare and had a positive impact in that it helped to achieve substantial results
(Helfferich 2011).
The development of interview guidelines was an iterative process and theguidelines changed slightly in the course of this research. To create the guidelines
all questions that could potentially help to answer the research questions were
written down randomly. As a second step, every question was evaluated to check
its contribution and to sort the questions accordingly (Helfferich 2011). The key
interview questions were identified in this step. In general, the interview guidelines
were divided into the following sections: general questions to the interviewee,
general information about the circular economy approach of the organization,
questions regarding the economic impacts, questions regarding success factors and
questions regarding the future perspective of circular economy in the organization.
The closing question gave the interviewee the chance to express his own relevance
and reflect on the interview (Helfferich 2011).
Besides the interviews, secondary data was collected for this research project.Yearly corporate reports and other internet documents, such as points of views