|M.Sc Student||Vinitsky Leon|
|Subject||Development of Sequential Testing for Checking Resolution|
of Measuring Devices
|Department||Department of Quality Assurance and Reliability||Supervisor||Dr. Yefim Haim Michlin|
For a certain class of instruments and devices, the serviceability - check requirements are formulated in terms of the probability of distinction between two specific states of the measured objects. Checking a device from this viewpoint can be expensive and necessitates a very large sample size (number of measurements), so that the tests may prove unprofitable. Accordingly, a methodology based on sequential testing and permitting reduction of the necessary sample size, is presented here for the class of devices in question.
Extensive information on the fixed-sample- size test (FSST) is available in literature, including a solution for the sample size on which a favorable decision, with the requisite error values, is to be based. In examining the available solution and algorithm, a mistake was detected. Although the final results do not differ significantly from those by the existing algorithm, especially in cases where the error is excessively small or excessively large - the method proposed here yields more accurate results while avoiding a complicated process.
The probability distributions of the number of measurements up to a positive/negative serviceability decision - were obtained, referred to the first - and second - kind errors. These distributions, especially the most decision wise - problematic interval, have long “tails” extending far beyond the necessary sample size for tests with a fixed size. Accordingly, a criterion was proposed for early termination of the tests, thereby significantly reducing the average number of measurements up to a decision. The dependences of the averages for the conditions in question were constructed, and in conjunction with the operating characteristic permit selection of the basic test parameters for a specific device. The proposed methodology and selection procedure are a major factor in ensuring the quality of measuring equipment.