measurement uncertainty workshop · 2019. 11. 7. · measurement uncertainty workshop • welcome...
TRANSCRIPT
MEASUREMENT UNCERTAINTY WORKSHOP
Lab Accreditation Meeting St. Petersburg, FL.
Jan. 24th 2017
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Measurement Uncertainty Workshop
• Welcome
• Sue Humphries, Acting Quality System Manager, Office of Regulatory Affairs, Pacific Regional Laboratory Northwest, U.S. Food and Drug Administration
• Patricia Hanson, Biological Administrator l-Microbiology Supervisor, Bureau of Food Laboratories, Florida Dept. of Agriculture and Consumer Services
• Heidi Hickes, Bureau Chief, Analytical Laboratory Bureau, Montana Dept. of Agriculture
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Outline•What is Measurement Uncertainty (MU)
•Why does ISO 17025 care about MU
•ISO17025 requirements
•Microbiology/Chemistry MU examples applied in real LAB setting
•Volunteers for hands on MU determinations
•Take Away MU messages
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What is Measurement Uncertainty ?
•When repeated measurements give different answers
•How widely spread are the values—wiggle room
•Judge quality of measurement from the spread
•Measure AVERAGE and STDEV in EXCEL
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What is Measurement Uncertainty ?
•Standard deviation-quantify spread
•STDEV expressed in units measuring
•%RSD: Relative Standard Deviation
•%RSD=divide STDEV by AVERAGE multiply by 100
•Universal Unit
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Why does ISO 17025 care?
•Measurements are subject to errors.
• Measurements have uncertainty associated with it.
•Result is incomplete without a statement of MU.
• Without MU give wrong impression to customer
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ISO 17025 Requirements
•Requires MU be estimated for your method
• Requires procedures to estimate MU
• Identify all components of uncertainty
• Follow conventional methods
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ISO 17025 Requirements
• Make Reasonable estimation of MU
• Express uncertainty values consistently and properly
• Ensure report does not give wrong impression of uncertainty
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ISO 17025 Requirements
• Need to put a number to the uncertainty
• Understandable and relevant
• You do not have to hire a statistician!
• Reasonable estimation based on method
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Practical and User Friendly
•Become familiar with uncertainty language
•Become familiar with basic steps
• Follow conventional methods
•Make a Reasonable Estimation
• Traceable: others need to understand what was done
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“A person who never made a mistake never tried anything new.”
Albert Einstein
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Take Aways• ISO requires MU be determined for each method
• ISO require procedures for determining MU
• Follow conventional methods
• Expressed properly
• Understandable and usable
• Traceable
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