This note intends to offer clarification on what the Measurement of Uncertainty (MU) is, and why it is required of certified laboratories. MU is required per the standard of the ISO/IEC 17025:2017 accreditation, which is the international standard that all quality labs follow. MU is an estimate of the possible error that can happen when performing analytical testing. Each analytical instrument (pipette, scale, HPLC, etc.) used during a testing process for a single sample has a margin of error in regards to accuracy. The margin of error for each instrument used throughout the testing process is carefully calculated, recorded and combined to form a Total Measurement of Uncertainty. This Total Measurement of Uncertainty represents the total possibility for error in your final testing results. The MU is displayed on your COA for each type of testing performed. MU is displayed as a +/- of a percentage. A total MU of +/- 5% of a final test result of 70% would mean that your final test result of 70% could truly lie anywhere between 66.5% to 73.5%. Potentially if you had a final result of 100% with an MU of +/- 5% your test result of 100% could “scientifically speaking” lie anywhere between 95% to 105%.

MU is set at a 95% Confidence Level per the ISO/IEC 17025:2017 accreditation standard. What is a Confidence Level? The Confidence Level is a statistical function used when calculating the MU for each individual analytical instrument used in the testing process and then used to calculate the Total Measurement of Uncertainty.

MU can be helpful when dealing with regulatory action limits set by government agencies. The USDA factors in the MU for final lab testing results. If you have a hemp sample that is .31% d9-THC (over the legal limit) with a MU of +/- 5%, the final test result of .31% could truly lie anywhere between .295% to .323% and therefore would be compliant.

From the Laboratory Testing Guidelines U.S. Domestic Hemp Production Program:

“Laboratories shall calculate and include the Measurement of Uncertainty (MU) when they report THC concentration test results. “Measurement of uncertainty” is defined as “the parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the particular quantity subject to measurement.” USDA does not establish or standardize an upper or lower boundary for general use by laboratories to calculate a measurement of uncertainty. MoU is typically not standardized, but rather is controlled using test methods controlled by performance standards (e.g., AOAC Standard Method Performance Requirements 2019.003 that can be found at https://www.aoac.org/resources/smpr-2019003/).”