Farm Scale Evaluations of spring-sown genetically modified herbicide-tolerant crops: a statistical assessment.

ABSTRACT: Primary results from the Farm Scale Evaluations (FSEs) of spring-sown genetically modified herbicide-tolerant crops were published in 2003. We provide a statistical assessment of the results for count data, addressing issues of sample size (n), efficiency, power, statistical significance, variability and model selection. Treatment effects were consistent between rare and abundant species. Coefficients of variation averaged 73% but varied widely. High variability in vegetation indicators was usually offset by large n and treatment effects, whilst invertebrate indicators often had smaller n and lower variability; overall, achieved power was broadly consistent across indicators. Inferences about treatment effects were robust to model misspecification, justifying the statistical model adopted.

SUBMITTER: Clark SJ 

PROVIDER: S-EPMC1560020 | biostudies-literature | 2006 Jan

REPOSITORIES: biostudies-literature