ABSTRACT
Renewal theory may be regarded as a branch of reliability theory. It was developed by mathematical statisticians in the years immediately following the Second World War in response to practical problems concerning the renewal of faulty components. The subject expanded so rapidly that it soon became unintelligible to the people it was meant to help. However, the ideas involved are quite simple, and many useful results may be obtained by straightforward arithmetic, which may most conveniently be incorporated in a spreadsheet developed on a personal computer.
