Research objective Research strategy

6.3.5 Case selection

Fourteen Dutch retailers were selected from the set of candidate cases. Retailers with different competitive strategies were selected: discounters lower end of the market, retailers that focus on cost middle segment of the market, and retailers that focus on response or differentiation higher end of the market. This attempt to select a “representative” sample of cases also shows that the study was designed as a parallel case study. This representativeness was not needed for this study.

6.3.6 Hypotheses

Because the proposition in this study specified a deterministic relation, and implicitly a continuously increasing relation, the hypothesis stated that the rank order of measurement points according to the observed values of the dependent variable was exactly the same as the rank order of meas- urement points according to the observed values of the independent vari- able. Because the independent variable time access window pressure had two independent dimensions, number of time window restricted areas and time window length, two hypotheses needed to be formulated.

6.3.7 Measurement

In order to generate realistic roundtrip data for all retailers under the conditions defined by the 18 scenarios, actual current roundtrip data needed to be collected. It is described how multiple data sources were used, namely interview data face-to-face, e-mail, telephone, question- naire data, and documents. The quality of the collected data cannot be evaluated because no further detail is provided. The four dimensions of distribution costs for all 14 cases in all conditions defined by the 18 scenarios were generated by a mathematical model. A reference is pro- vided to another article in which the model is described and discussed in more detail.

6.3.8 Data presentation

Figure 6.2 presents the data generated for the different scenarios in one case, as an example. The mode of presentation is such that it directly provides the rank orders needed for testing the hypothesis.