Variability associated with the official USDA sampling plan used to inspect export wheat shipments for Tilletia controversa spores

The variability associated with estimating the true concentration of teliospores of dwarf bunt (Tilletia controversa) per 50 g of wheat (TC concentration) in an export wheat shipment was studied by measuring the TC concentration in 16 test samples (50 g) taken from each of 137 export shipments. The...

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Bibliographic Details
Published in:Plant pathology 2001-12, Vol.50 (6), p.755-760
Main Authors: Whitaker, T. B., Wu, J., Peterson, G. L., Giesbrecht, F. G., Johansson, A. S.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Cereal and baking product industries
dwarf bunt
Food industries
Fundamental and applied biological sciences. Psychology
Fungal plant pathogens
Generalities. Techniques
Phytopathology. Animal pests. Plant and forest protection
sampling
Tilletia controversa
variability
wheat
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Summary:The variability associated with estimating the true concentration of teliospores of dwarf bunt (Tilletia controversa) per 50 g of wheat (TC concentration) in an export wheat shipment was studied by measuring the TC concentration in 16 test samples (50 g) taken from each of 137 export shipments. The variability among the 16 TC test sample results, as measured by the standard deviation, was found to increase with TC concentration. The functional relationship was approximately linear in a full‐log plot and regression analysis was used to determine the coefficients of the regression equation. Using statistical theory, the regression equation was modified to predict the standard deviation among test sample sizes other than the 50 g size used in this study. The standard deviation and coefficient of variation associated with using a 50 g test sample to estimate the true TC concentration of a wheat shipment with 2000 spores per 50 g were estimated to be 1062·8 and 53·1%, respectively. Increasing test sample size to 1600 g reduced the standard deviation and coefficient of variation to 187·9 and 9·4%, respectively.
ISSN:0032-0862
1365-3059
DOI:10.1046/j.1365-3059.2001.00640.x