ASME B89.7.4.1:2005 pdf download Measurement Uncertainty and Conformance Testing: Risk Analysis
1 SCOPE
This Technical Report provides guidelines for settinggauging (or test) limits in support of accept/reject decisions in workpiece inspections, instrument verificationsand general conformance tests where uncertain numerical test results are compared with specified requirements.
In accepting or rejecting workpieces or instrumentsbased on the results of inspection measurements, thepresence of unavoidable measurement uncertainty introduces the risk of making erroneous decisions. By implementing a decision rule that defines a range of acceptablemeasurement results, one can balance the risks ofrejecting conforming workpieces or instruments andaccepting nonconforming ones.
2 DEFINITIONS AND TERMINOLOGY
For the purposes of this Technical Report, the follow-ing definitions apply [1- 4]:
accept- reject measurement measurement made for thepurpose of accepting or rejecting a workpiece, workpiece feature, or measuring instrument [4].acceptance. decision that the measured value of a charac-teristic satisfies the acceptance criteria
acceptance criterion. specification criterion for acceptanceof a workpiece, workpiece feature or measuring instrument based upon the result of a measurement or test
NOTE: The most common acceptance criterion for accept/rejectdecisions is acceptance when the measured characteristic lies inthe acceptance zone and rejection otherwise.
acceptance zone’ set of values of a characteristic, for aspecified measurement process and decision rule, thatresults in product acceptance when a measurementresult is within this zone [3].
binary decision ru/e. decision rule with only two possibleoutcomes, either acceptance or rejection [3].
characteristic. property that helps to identify or differentiate between items of a given population [5, para, 1.5.11.In this Report, a characteristic is typically a workpiecefeature or the error of a measuring instrument subjectto a conformance test.
conformance test; measurement of a characteristic in orderto decide conformance or nonconformance with specifi-cations.
conforming: a characteristic is conforming if its true valuelies within or on the boundary of the tolerance zone.NOTE: In ASME B89.7.2-1999, conforming is defined as having ameasured value lying within or on the boundary of the allowabletolerance band. This definition would be correct if measured werechanged to true.
consumer’s risk: probability of a pass (or Type Il) error.(The cost of such an error is generally borne by theconsumer.)
decision ru/e: documented rule that describes how mea-surement uncertainty will be allocated with regard toaccepting or rejecting a product according to its specifi-cation and the result of a measurement [3].fai/ error: rejection, as a result of measurement error,of a characteristic whose true value is within specifiedtolerances (also known as a Type I error) [4].gauging /imits. specified limits of a measured value [4].quard band: magnitude of the offset from a specificationlimit to an acceptance or rejection zone boundary [3].inspection. activities such as measuring, examining, test-ing, and gauging one or more characteristics of a productor service, and comparing with specified requirementsto determine conformity [5, para. 1.2.1].inspection by variab/es. method that consists in measuringa quantitative characteristic for each item of a popula-tion or a sample taken from this population [6, para. 3.1].
ASME B89.7.4.1:2005 pdf download
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