In ordinary life "reliability" is an ephemeral but desirable property of a machine or service that is generally judged in a very subjective manner. But for an engineer, reliability has large financial implications in terms of maintenance policies, running costs, and spares stockholding. In safety critical situations (transport or military equipment), the implications are wider; therefore, it is very important to be able to quantify reliability. This book is an introduction to reliability analysis. Since it is aimed at engineers, it begins by assuming no prior statistical knowledge. It teaches by example taken from engineering problems. Exercises are built around real machines and events, and the solutions given illuminate the subject. It is the first book of its kind aimed at those for whom reliability analysis has far-reaching consequences.