Economic quality inspection procedures with screening variables

Abstract

Economic screening and acceptance sampling inspection procedures are considered for situations where the quality of each item is characterized by a performance variable whose measurement requires expensive and/or destructive testing. A variable that is correlated with the performance variable is utilized in the screening process. In acceptance sampling, sampling inspection is based on the performance variable and screening inspection of rejected lots is based on the screening variable. Three decision criteria are used; acceptance, screening and scrapping. scrapping. An economic attributes acceptance sampling plan is given for situations where both variables are dichotomous. Assuming that misclassification error rates involved in the screening process are known, linear cost model is constructed and methods for finding optimal sampling plans are presented for both beta-binomial and double-binomial priors. For situations where these variables are jointly normally distributed, economic screening procedures for increasing the outgoing quality are given both for the case where all parameters are known and for the case involving some unknown parameters. Using the results obtained from these screening procedures an economic variables acceptance sampling plan is presented. Linear cost model is constructed and a method for finding optimal sampling plan is developed under normal prior. Comparative studies are also made between the acceptance sampling procedures involving three decisions and the procedures using only two decisions.