Cohort studies
A cohort study takes a group of individuals and usually follows them forward in time, the aim being to study whether exposure to a particular aetiological factor will affect the…
Regression methods for clustered data
Various regression methods can be used for the analysis of the two-level hierarchical structure described in Chapter 41, in which each cluster (level 2 unit) contains a number of individual…
Case–control studies
A case–control study compares the characteristics of a group of patients with a particular disease outcome (the cases) to a group of individuals without a disease outcome (the controls), to…
Numerical data: a single group
19 Numerical Data: a Single Group The Problem We have a sample from a single group of individuals and one numerical or ordinal variable of interest. We are interested in…
Categorical data: more than two categories
Chi-Squared Test: Large Contingency Tables The Problem Individuals can be classified by two factors. For example, one factor may represent disease severity (mild, moderate, severe) and the other factor may…
Categorical data: a single proportion
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…
Confidence intervals
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 analysis
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….
Multiple linear regression
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…
Theoretical distributions: the Normal distribution
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….
