Introduction

The importance of product reliability is greater than ever at the present time. As more and more products are introduced to the market, consumers now have the luxury of demanding high quality and long life in the products they purchase. In such a highly demanding and competitive market, one way by which manufacturers (of computers, automobiles, and electronic items, for example) attract consumers to their products is by providing warranties on product lifetimes. In order to design a cost-effective warranty, a manufacturer must have sound knowledge about product failure-time distributions. To gain this knowledge, life-testing and reliability experiments are carried out before (and while) products are put on the market. Of course, the information gained through life-testing experiments is also used for other purposes in addition to determining effective warranties; for example, in pharmaceutical applications, the lifetimes of drugs may be studied in order to determine appropriate dosage administration and expiry dates. Furthermore, continuous improvement of products becomes essential and even critical in a competitive market. Life-testing experimentation is one way by which product improvement and product quality can be gauged.