AOAC Method Validation (August 29, 2018)

RSD i

(Intermediate Precision)

Background X AOAC itself does not have any guidelines for intermediate precision. X ISO 5273- 3 section 0.6 describes four “likely conditions” for intermediate precision: time, operators, equipment, and calibration. X The imprecision contained in the ISO definition with its “likely conditions” severely reduces the utility of the resulting data. X RSDi, as defined by ISO, is somewhere between RSDr and RSDR, but is not clear where it is between RSDr and RSDR. Hence, there is little more one can say than that the RSDi should be less than RSDR. Since the term is so imprecise it appears there is little to be gained by including RSDi in SMPRs.

RSD i

(Intermediate Precision)

Background X An OMB Working Group created to consider the question of RSDi recommended the following: The RSDi of a method should not exceed 80% of the reproducibility standard deviation, or in AOAC’s case, no more than 80% the performance requirement specified for the relative standard deviation of reproducibility (RSDR) in the applicable SMPR. A method that demonstrates an RSDi of greater than 80% should be investigated to determine the source(s) of variability and improved to reduce variability.