Introduction

In principle an investigation begins with the formulation of a research question or questions, or sometimes more specifically a research hypothesis. In practice, clarification of the issues to be addressed is likely to evolve during the design phase, especially when rather new or complex ideas are involved. Research questions may arise from a need to clarify and extend previous work in a field or to test theoretical predictions, or they may stem from a matter of public policy or other decision-making concern. In the latter type of application the primary feature tends to be to establish directly relevant conclusions, in as objective a way as possible. Does culling wildlife reduce disease incidence in farm animals? Does a particular medical procedure decrease the chance of heart disease? These are examples of precisely posed questions. In other contexts the objective may be primarily to gain understanding of the underlying processes. While the specific objectives of each individual study always need careful consideration, we aim to present ideas in as generally an applicable form as possible.