Sampling grain shipments to detect genetically modified seed.
Using the binomial distribution, the effect of sample size on the variability among sample test results when sampling a lot with 1.0% genetically modified (GM) or biotech seed was evaluated. The coefficient of variation, cv, among 500-seed sample test results taken from a lot with truly 1.0% was computed to be 44.5%. Increasing sample size to 1000 seeds reduced the cv among sample test results to 31.5%. The effects of sample size and accept/reject limits on the buyer's risk (bad lots accepted) and the seller's risk (good lots rejected) was also evaluated assuming a tolerance of 1.0% GM seed. Increasing sample size decreases both the buyer's and seller's risks at the same time. Using an accept/reject limit below the regulatory tolerance decreases the buyer's risk, but increases the seller's risk. Using an accept/reject limit above the regulatory tolerance decreases the seller's risk but increases the buyer's risk.
Whitaker
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USDA/ARS, North Carolina State University, Raleigh 27695-7625, USA. Tom_Whitaker@ncsu.edu
Freese
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Giesbrecht
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Slate
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D000704:Analysis of Variance; D002523:Edible Grain / Q000737:chemistry* / Q000235:genetics; D005504:Food Analysis / Q000379:methods* / Q000706:statistics & numerical data; D030841:Food, Genetically Modified; D018401:Sample Size; D012639:Seeds / Q000737:chemistry / Q000235:genetics