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The role of uncertainty of measurement in conformance testing. Steve Sidney Steve Sidney Consulting. Introduction Tolerance limits and intervals Acceptance limits Knowledge of the measurand Probability of conformance Consumer / producer risks Summary. Introduction - PowerPoint PPT Presentation
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Use of Control Charts in Laboratories
The role of uncertainty of measurement in conformance
testing
Steve SidneySteve Sidney Consulting
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Introduction• Tolerance limits and intervals• Acceptance limits• Knowledge of the measurand• Probability of conformance• Consumer / producer risks• Summary
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Introduction– What is conformity assessment– Inspection– Role of measurement– UoM – Probability– Decide if item conforms to specified
requirement– Risk
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Intervals and Limits
TL TU
AL AUAcceptance Interval
Tolerance Interval
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Probability & UoM
Probability D
ensity Function
Measured Quantity Value
Expanded Uncertainty 95% CI
Value of Measurand
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Knowledge of Measurand – GUM – Conditional PDF– Poor knowledge – broad PDF– Measurements sharpen PDF– Measurement effectively updates pre-
measurement (prior), yielding post measurement (posterior) & includes measurement data.
– Bayes theorem (conditional probability)
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Decisions to be made– Accept item– Reject item– Perform another measurement
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Consumer / Producer Risk– Valid Acceptance– False Acceptance– Valid Rejection– False Rejection
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Probability of conformance“True” Value
Measured Value
Limit
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
AAcceptance Interval
Tolerance IntervalGuard Band
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Risk
Valid Acceptance
False Rejection
Valid Rejection
False Acceptance
Limit
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
• Summary– Importance of UoM– Guidelines
BIPM JCGM 106 (Evaluation of measurement data – The role of MU in CA) http://www.bipm.org
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The role of uncertainty of measurement in conformance testing
T&M 2010 Conference & Workshop
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