The value of a datum – how little data do we need for a quantitative risk analysis ?

Aim Conservation managers are typically faced with limited resources, time and information. The philosophy underlying risk assessment should be robust to these limitations. While there is a broad support for the concept of risk assessments, there is a tendency to rely on expert opinion and exclude formal data analysis, possibly because available information is often scarce. When data analyses are conducted, often much simplified models are advocated, even though this means excluding processes believed by experts to be important. In this manuscript, we ask: should statistical analyses be conducted and decisions modified based on a single datum? How many data points are needed before predictions are meaningful? Given limited data, how complex should models be?