The skills to judge the validity of studies dealing with cause and effect relationships critically are a crucial requisite for career development in epidemiology, community medicine or public health.

This book proposes a scheme for the critical appraisal of epidemiological studies and trials. This approach starts by describing the methods and results. Then, it considers three possible non-causal explanations: “observation” bias, confounding and chance. This system forces the investigator or the reader to think about the quality of the data and design and to appraise critically whether a truly causal explanation can be accepted. The aim is to build a logical system of critical appraisal, to allow readers to evaluate studies and to carry out their own studies more effectively. …