CUSUM
CUSUM - A class of statistical procedures for assessing whether or not a process is in control. Each CUSUM value is constructed by accumulating incremental values obtained from observed results of the process, and then determined to either exceed or fall within acceptable limits for that process. The initial CUSUM values for each laboratory whose application for accreditation is accepted are set at zero. The CUSUM values are reset to zero at the beginning of each year; that is, the CUSUM values associated with the first maintenance check sample each year are set equal to the CUSUM increment for that sample. The four CUSUM procedures are:
(1) Positive systematic laboratory difference CUSUM (CUSUM-P) - monitors how consistently an accredited laboratory gets numerically greater results than the comparison mean;
(2) Negative systematic laboratory difference CUSUM (CUSUM-N) - monitors how consistently an accredited laboratory gets numerically smaller results than the comparison mean;
(3) Variability CUSUM (CUSUM-V) - monitors the average “total deviation” (i.e., the combination of the random fluctuations and systematic differences) between an accredited laboratory's results and the comparison mean; and
(4) Individual large deviation CUSUM (CUSUM-D) - monitors the magnitude and frequency of large differences between the results of an accredited laboratory and the comparison mean.
(i) Food chemistry - For the purposes of part 439, “food chemistry” will refer to analysis of raw or processed meat or poultry products for the analytes moisture, protein, fat, and salt. All four analytes must be determined when a food chemistry analysis is conducted, unless otherwise advised by the ALP.
(j) Individual large deviation - An analytical result that differs from the sample comparison mean by more than would be expected assuming normal laboratory variability.
(k) Initial accreditation check sample - A sample provided by the ALP to a non-Federal laboratory to determine whether the laboratory's analytical capability meets the standards for granting accreditation.
(l) Inter-laboratory accreditation maintenance check sample - A sample provided by FSIS to an accredited laboratory to assist in determining whether the laboratory is maintaining acceptable levels of analytical capability.
(m) Large deviation measure - A measure that quantifies an unacceptably large difference between a laboratory's analytical result and the sample comparison mean.
(n) Minimum proficiency level (MPL) - The minimum concentration of a residue at which an analytical result will be used to assess a laboratory's quantification capability. This concentration is an estimate of the smallest concentration for which the average coefficient of variation (CV) for reproducibility (i.e., combined within and between laboratory variability) does not exceed 20 percent.
(o) Minimum reporting level (MRL) - The number such that if any obtained analytical value for a residue in a check sample or official sample equals or exceeds this number, then the residue is reported together with the obtained analytical value.
(p) Official sample - A sample selected by an inspector or inspection service employee in accordance with FSIS procedures for regulatory use.
(q) Probation - The period commencing with official notification to an accredited laboratory that its check sample results no longer satisfy the performance requirements specified in this rule, and ending with official notification that accreditation either is fully restored, is suspended, or is revoked.
(r) QA (See Quality assurance recovery).
(s) QC (See Quality control recovery).
(t) Quality assurance (QA) recovery - The ratio of a laboratory's analytical value for a check sample residue to the established level of the analyte in the check sample, multiplied by 100. As dictated by the procedures for the analyte, the analytical value may be adjusted prior to the recovery computation.
(u) Quality control (QC) recovery - The ratio of a laboratory's analytical value of a quality control standard to the established level of the analyte in the standard, multiplied by 100. As dictated by the procedures for the analyte, the analytical value may be adjusted prior to the recovery computation.
(v) Refusal of accreditation - An action taken by FSIS when a laboratory that is applying for accreditation is denied the accreditation.
(w) Responsibly connected - Any individual, or entity, that is a partner, officer, director, manager, or owner of 10 percent or more of the voting stock of the applicant or recipient of accreditation or an employee in a managerial or executive capacity or any employee who conducts or supervises the chemical analysis of FSIS official samples.
(x) Revocation of accreditation - An action taken by FSIS against a laboratory, removing the laboratory's right to analyze official samples.
(y) Standardizing constant - A number that results from a mathematical adjustment to the “standardizing value” and is used to compute the standardized difference for a check sample result. The number takes into consideration the expected variance of the difference between the accredited or applying laboratory's result(s) and the comparison mean for a sample, the standardizing value, the correlation and number of repeated results by a laboratory on a sample, and the number of laboratories that analyzed a sample.
(z) Standardized difference - The quotient of the difference between a laboratory's result on a sample and the comparison mean of the sample divided by the standardizing constant.
(aa) Standardizing value - A number representing the performance standard deviation of an individual result. The number is given, or computed by, the information provided in Tables 1 and 2 to this paragraph (aa).
Source
9 CFR § 439.1
Scoping language
Accreditation - Determination by FSIS that a laboratory is qualified to analyze official samples of raw or processed meat and poultry products, because it has met the requirements for accreditation specified in this part, for the presence and amount of all four food chemistry analytes (protein, moisture, fat, and salt); or a determination by FSIS that a laboratory is qualified to analyze official samples of raw or processed meat and poultry products, because it has met the requirements for accreditation in this part, for the presence and amount of a specified chemical residue of any one of several classes of chemical residues. A laboratory may hold more than one accreditation.