TABLE 1.

Comparison of activities in definitive and WoE approaches to risk assessment.

Task	Definitive	Weight of evidence	Comments
Define protection goals	Identify the reason for conducting the risk assessment and the decision that the risk assessment will inform	Identify the reason for conducting the risk assessment and the decision that the risk assessment will inform	An unclear purpose may result in unfocussed data gathering that appears similar to a weight of evidence approach to risk assessment
Operationalise protection goals and set assessment endpoints	Define exactly what the risk assessment aims to protect and what the risk assessment will predict	Define exactly what the risk assessment aims to protect and what the risk assessment will predict	Difficulty in defining operational protection goals or assessment endpoints may result in unfocussed data gathering that appears similar to a weight of evidence approach to risk assessment
Define risk hypotheses	Formulates at least one hypothesis that is quantitative and incorporates a clear decision-making criterion	Formulates hypotheses that tend to be qualitative or semi-quantitative Not possible to formulate a hypothesis such that its corroboration or falsification is possible by a single test	An example of a quantitative hypothesis incorporating a decision-making criterion is LC50/EEC ≥ 1 An example of a semi-quantitative hypothesis is that the rate of hybridisation between a GM crop and a wild species will be no greater than the rate between similar non-GM crops and the wild species
Test risk hypothesis	The results are widely applicable; they are largely independent of local conditions The test is powerful and repeatable	The results apply only to the specific times or locations at which the test was performed The test is weak and its results are difficult to reproduce	Data from laboratory ecotoxicology studies are widely applicable Data on crop hybridisation rates may depend on local conditions (occurrence of sexually compatible species, weather etc.)