A study on truncated life tests through acceptance sampling procedures

Reliability of a unit (or product) is the probability that the unit performs its intended function adequately for a given period of time under the stated operating conditions or environment. By a unit we mean an element, a system or a part of a system, or the like. An acceptance sampling is concerned with the decision to accept or reject a lot. The design of the acceptance sampling process includes decisions about sampling versus complete inspection. Management can select the best plan by using operating characteristics values of different sampling plans using lifetime distributions. Chapter 1 comprises of basic concepts of quality control, acceptance sampling, reliability, lifetime distributions and the review of sampling plans which are relevant to this thesis. In Chapter 2, double sampling plan for truncated life test is proposed when the lifetime of the test items follows different lifetime distributions. Probability of acceptance is calculated for different consumer’s confidence levels. Probability of acceptance and producer’s risk are analyzed with the help of tables and examples. In Chapter 3, a hybrid group acceptance sampling plan for a truncated life test is proposed when the lifetime of the test items follows different lifetime distributions. The minimum number of testers, r is determined when the consumer’s risk, the termination time multiplier and the group size are specified. The operating characteristic values for various confidence levels are also obtained. In Chapter 4, a weighted group acceptance sampling plan for a truncated life test is proposed when the lifetime of an item follows different lifetime distributions. The minimum number of groups required for a given group size and the acceptance number is determined when the consumer’s risk and the test termination time are specified. The operating characteristic values for various quality levels are obtained. The results are explained with examples. In Chapter 5, a two – stage group acceptance sampling plan for truncated life test is proposed when the lifetime of an item follows different lifetime distributions. The minimum number of groups required is determined when the consumer’s risk and the test termination time are specified. The operating characteristic values for various quality levels are obtained. The results are explained with examples. In Chapter 6, a repetitive group acceptance sampling plan for a truncated life test is proposed when the lifetime of an item follows different distributions. The minimum sample size required is determined when the consumer’s risk and the test termination time are specified. The operating characteristic values according to various quality levels are obtained. The results are explained with examples. In Chapter 7, a conditional repetitive group acceptance sampling plan for a truncated life test is proposed when the lifetime of an item follows different distributions. The sample sizes required for the acceptance numbers are determined when the consumer’s risk and the test termination time are specified. The probability of acceptance with respect to various confidence levels is obtained. The results are explained with examples.