Tolerances of the International Seed Testing Association regarding the dispersion of germination test replicate results are based on the theoretical variance of a binomial sample. Several publications over the last 60 years give evidence that the dispersion between replicate results
is in practice smaller than this theoretical variance. This article investigates in detail, whether this phenomenon indeed exists and if yes, what are the causes. Simulations show that the theoretical reference formula used up to now for the quantification of dispersion and for the establishment
of tolerances is correct if sampling is at random and the evaluation unbiased. Nevertheless, the four empirical replicate results of a germination test show on average, without rounding of their mean germination percentage, a statistically significant underdispersion. The laboratory where
the test was conducted had the highest influence on this underdispersion within a given species. These findings indicate clearly that current procedures for the germination test, whereby the four replicates are evaluated by hand usually by the same person, cause a bias and this bias causes
underdispersion. To avoid this and improve the correctness of the current tolerances, replicates of germination tests should be blinded and or tested by different seed analysts.
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Document Type: Research Article
July 1, 2016
This article was made available online on July 4, 2016 as a Fast Track article with title: "Underdispersion of replicate results in germination tests is species and laboratory specific".
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Seed Science and Technology (SST) is one of the leading international journals featuring original papers and review articles on seed quality and physiology as related to seed production, harvest, processing, sampling, storage, distribution and testing. This widely recognised journal is designed to meet the needs of researchers, advisers and all those involved in the improvement and technical control of seed quality.
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