Essential statistics and epidemiology

This chapter provides a grounding in basic statistics, descriptive epidemiology, analytical epidemiology, and hypothesis testing appropriate for health protection practitioners. The analysis of categorical data using frequency distributions, and charts, and the interpretation of epidemic curves is described. The description of quantitative data including central tendency, standard deviation, and interquartile range is concisely explained. The role of geographical information systems and different disease map types is used to demonstrate how disease clusters may be detected. Determining possible association between specific risk factors and outcome is described in the section on analytical epidemiology, using the risk ratio and the odds ratio. The use of these in different study/investigation types is explained. The importance of confounding, matching, and standardization in study design is described. The final part of the chapter covers hypothesis testing to distinguish between real differences and chance variation, and the use of confidence intervals.