Random sampling error Statistical significance: could an apparent association have arisen by chance? Confidence intervals The relationship between p-values and confidence intervals Power: could we have missed a true association?…
What is a systematic review? Identifying the literature Publication and related biases Study inclusion and exclusion Appraising the literature Summarising the data Graphical display of results Assessing heterogeneity Meta-analysis Pooled…
The research question and study design Internal validity The study sample: selection bias Example 1:case–control studies of blood transfusion and Creutzfeldt–Jakob disease Example 2:a case–control study of oesophageal cancer and…
Chapter 5Cross-sectional studies 5.1 Purpose Cross-sectional studies are usually the simplest observational studies to conduct and analyse. They are often used to describe (summarise) the characteristics, habits, or opinions of…
Chapter 2Outcome measures, risk factors, and causality This chapter describes the three fundamental types of measurements used in observational studies and how data based on each type are summarised and…
Chapter 3Effect sizes Before presenting types of observational studies (Chapter 5–8), it is worth knowing how they are analyzed. Examining the effect of an exposure (including risk factors) on an…
Chapter 10Systematic reviews and meta-analyses Chapters 5–8 provide an overview of the design and analysis of individual observational studies. Systematic reviews combine results from several published or unpublished studies, and…
Chapter 9Prognostic markers for predicting outcomes Many observational studies aim to examine the association between an exposure and outcome. A special case of this is to develop a model using…
Chapter 4Regression analyses The main limitation of most of the simple statistical methods in Section 3.4 is that they can only examine the relationship between one exposure and one outcome…
Chapter 6Case–control studies 6.1 Purpose Case–control studies are generally considered to be the next most reliable study design after cohort studies when evaluating risk factors and causality (Chapter 1, page…
