This paper presents the case of the UK government as evidence-based. Evidence based policy has become a major part of the government's approach to policy making and the machinery of government. The paper attempts to define evidence-based policy and considers the role of evidence in the policy-making process. It presents a thorough examination of the different types of evidence in use, the methods used for gathering and appraising, with best practice examples.

What is Evidence-Based Policy?
EDP is a 'rigorous approach that gathers, critically appraises and uses high quality research evidence to inform policy making and profession practice.' Davies compares this to 'opinion-based policy, which relies heavily on either the selective use of evidence (e.g. on single studies irrespective of quality) or on the untested views of individuals or groups, often inspired by ideological standpoints, prejudices, or speculative conjecture.'

The paper goes onto consider other factors, other than evidence, which influence policy making and policy implementation. These include the experience, expertise and judgment of policy officials and Ministers, values and ideology, available resources, habits and tradition, lobbyists, pressure groups and the media, and the pragmatics and contingencies of everyday political life (see fig. 2). The paper considers the challenges that these competing factors raise for government, evaluation and analysis are also considered. Finally the paper reviews what is known about the mechanisms that need to be in place for evidence-based policy making to be effective.