טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentVinitsky Leon
SubjectDevelopment of Sequential Testing for Checking Resolution
of Measuring Devices
DepartmentDepartment of Quality Assurance and Reliability
Supervisor Dr. Yefim Haim Michlin


Abstract

            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.