It has been argued that the central role of research design is to
minimize the chance of drawing incorrect causal inferences from data.
Design is a logical task undertaken to ensure that the evidence collected
enables us to answer questions or to test theories as unambiguously as
possible. When designing research it is essential that we identify the type
of evidence required to answer the research question in a convincing
way. This means that we must not simply collect evidence that is consistent
with a particular theory or explanation. Research needs to be
structured in such a way that the evidence also bears on alternative rival
explanations and enables us to identify which of the competing explanations
is most compelling empirically. It also means that we must not
simply look for evidence that supports our favourite theory: we should
also look for evidence that has the potential to disprove our preferred
explanations.