The Problem We have a single sample of n individuals; each individual either ‘possesses’ a characteristic of interest (e.g. is male, is pregnant, has died) or does not possess that…

Once we have taken a sample from our population, we obtain a point estimate (Chapter 10) of the parameter of interest, and calculate its standard error to indicate the precision…

Survival data are concerned with the time it takes an individual to reach an endpoint of interest (often, but not always, death) and are characterized by the following two features….

What is It? We may be interested in the effect of several explanatory variables, x1, x2, …, xk, on a response variable, y. If we believe that these x’s may…

In Chapter 4 we showed how to create an empirical frequency distribution of the observed data. This contrasts with a theoretical probability distribution which is described by a mathema­tical model….

Rates In any longitudinal study (Chapter 12) investigating the occurrence of an event (such as death), we should take into account the fact that individuals are usually followed for different…

Clustered data conform to a hierarchical or nested structure in which, in its simplest form (the univariable two-level structure), the value of a single response variable is measured on a…

The Systematic Review What Is It? A systematic review1 is a formalized and stringent process of combining the information from all relevant studies (both published and unpublished) of the same…

Summarizing Data It is very difficult to have any ‘feeling’ for a set of numerical measurements unless we can summarize the data in a meaningful way. A diagram (Chapter 4)…

Summarizing Data If we are able to provide two summary measures of a continuous variable, one that gives an indication of the ‘average’ value and the other that describes the…