Statistics is a practical discipline that attempts to answer real-life questions about problems in a variety of application areas, based on relevant data. Many statistical courses focus on the statistical methods that are used to analyse such data, but these statistical methods are underpinned by a body of theory that explains why they work.

Statistical theory explains the circumstances in which 'standard' statistical methods work, and when they are likely to break down or be misleading. The theory also provides techniques that might be used to extend standard statistical methods when the assumptions underlying them are violated.

Mathematics is used to describe statistical theory. In particular, a sound background in algebra and calculus (differentiation and integration) is required before attempting to study this e-book.