Effective sample sizes and test duration for life testing

Today´s global economy in a shrinking world is causing many companies to look for new or untapped areas to achieve a competitive advantage. They are faced with a consumer who is better educated, more knowledgeable, and more demanding when selecting products to purchase. These consumers have instant access to product data via the Internet and the mass media. They are examining the products with critical skepticism and rejecting the purchase of any item that does not meet their expectations. To meet this critical examination, the manufacturers must ensure that they recognize the proper buyer characteristics, offer a product that will pass such customer scrutiny, and achieve a reputation of building a quality product. One area ripe for product improvement is useful product life. This means testing the product to ensure we know what the life characteristics and the failure modes are so effective improvements can be made. Whenever life testing is discussed, one of the first questions posed in every discussion is how many units do I test and how long do I test them. This paper shows how to determine the answers to these questions to obtain meaningful data and cost effective testing