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1.
Anal Bioanal Chem ; 414(2): 1105-1114, 2022 Jan.
Article in English | MEDLINE | ID: mdl-34713313

ABSTRACT

The relationship between reproducibility standard deviation and mass fraction in food analysis has been studied in compilations of statistics from collaborative trials and from proficiency tests. There was a broad tendency for both categories of statistics to follow the Horwitz function although systematic deviations from it were easily detected at both extremes of the mass fraction range (below 10-7 and above 10-2). The two compilations were found to have very similar properties over the whole range of mass fractions, that is from about 10-10 (0.1 ppb) upwards. This similarity has implications for the determination of detection limit.


Subject(s)
Food Analysis/methods , Reference Standards , Reproducibility of Results
2.
J AOAC Int ; 89(1): 232-9, 2006.
Article in English | MEDLINE | ID: mdl-16512253

ABSTRACT

The study considers data from 2 UK-based proficiency schemes and includes data from a total of 29 rounds and 43 test materials over a period of 3 years. The results from the 2 schemes are similar and reinforce each other. The amplification process used in quantitative polymerase chain reaction determinations predicts a mixture of normal, binomial, and lognormal distributions dominated by the latter 2. As predicted, the study results consistently follow a positively skewed distribution. Log-transformation prior to calculating z-scores is effective in establishing near-symmetric distributions that are sufficiently close to normal to justify interpretation on the basis of the normal distribution.


Subject(s)
Data Interpretation, Statistical , Organisms, Genetically Modified , Food Analysis , Food, Genetically Modified , Likelihood Functions , Models, Statistical , Normal Distribution , Polymerase Chain Reaction , Reproducibility of Results , Statistical Distributions
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