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The following competition was organized by the Business Section of the Netherlands Society for Statistics and Operations Research (VVS): maxi mize the output of a given simulation model by selecting the best combination of six inputs; only 32 runs are permitted. Twelve teams competed; these teams came from industry and academia. This paper is written by the winning team, ex plaining its design and analysis. That design pro ceeded in stages. First, a special design was used to estimate all main effects and two-factor inter actions (namely, Rechtschaffner's saturated de sign). Then quadratic effects were estimated by changing factors one at a time. Finally, the re sulting estimated second-order polynomial was used to estimate the optimal input combination. The paper presents a combination of design of ex periment techniques and common sense that may have more applications in solving real problems.

Systems thinking inventory tasks have been developed to assess people's understanding of basic system concepts. Since 2000, these tasks have been used with different populations of students ranging from high school to MBA. The results have consistently shown that people have poor understanding of system concepts. This article focuses on the effects of an introductory system dynamics course on the performance with three of the systems thinking inventory tasks, i.e. department store, manufacturing, and CO 2 zero emissions tasks. Students answered the questions before and after a course that takes 13 weeks. The performance in pre-and post-tests and the changes in performance, as well as the implications for further research, are discussed.

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Escalation of commitment, the tendency of decision makers to keep on investing in losing courses of action, has been shown to be a costly decision bias that affects many areas of decision making. Even though escalation is a widely studied phenomenon, there has been comparatively little research on how to avoid this bias. The present study focuses on de-escalation of commitment and proposes that causal loop diagrams (CLDs) can help to decrease escalating commitment to a failing course of action. By means of an experiment, this study shows that using a CLD decreases escalation tendencies.