ABSTRACT
Survival analysis is the phrase used to describe the analysis of data in the form of times from a well-dened time origin until the occurrence of some particular event or end-point. In medical research, the time origin will often correspond to the recruitment of an individual into an experimental study, such as a clinical trial to compare two or more treatments. This in turn may coincide with the diagnosis of a particular condition, the commencement of a treatment regimen or the occurrence of some adverse event. If the endpoint is the death of a patient, the resulting data are literally survival times. However, data of a similar form can be obtained when the end-point is not fatal, such as the relief of pain, or the recurrence of symptoms. In this case, the observations are often referred to as time to event data, and the methods for analysing survival data that are presented in this book apply equally to data on the time to these end-points. The methods can also be used in the analysis of data from other application areas, such as the survival times of animals in an experimental study, the time taken by an individual to complete a task in a psychological experiment, the storage times of seeds held in a seed bank or the lifetimes of industrial or electronic components. The focus of this book is on the application of survival analysis to data arising from medical research, and for this reason much of the general discussion will be phrased in terms of the survival time of an individual patient from entry to a study until death.
1.1 Special features of survival data
