Statistical Aspects of Environmental Risk Assessment of GM Plants for effects on Non-Target Organisms

Previous European guidance for environmental risk assessment of genetically modified plants emphasized the
concepts of statistical power but provided no explicit requirements for the provision of statistical power analyses.
Similarly, whilst the need for good experimental designs was stressed, no minimum guidelines were set
for replication or sample sizes. Furthermore, although substantial equivalence was stressed as central to risk
assessment, no means of quantification of this concept was given. This paper suggests several ways in which
existing guidance might be revised to address these problems. One approach explored is the ‘bioequivalence’
test, which has the advantage that the error of most concern to the consumer may be set relatively easily.
Also, since the burden of proof is placed on the experimenter, the test promotes high-quality, well-replicated
experiments with sufficient statistical power. Other recommendations cover the specification of effect sizes,
the choice of appropriate comparators, the use of positive controls, meta-analyses, multivariate analysis and
diversity indices. Specific guidance is suggested for experimental designs of field trials and their statistical
analyses. A checklist for experimental design is proposed to accompany all environmental risk assessments.