We discuss anew the very often worked question of the respective virtues of quantitative and qualitative surveys by a novel approach consisting of reasoning on a simplified conceptual model in order to identify philosophical questions about the real cases. This conceptualization is described in detail and leads to clear delineation of quantitative and qualitative approaches. This demonstrates in some situations a real contradiction between images provided by the two methods. This is illustrated by some examples, including the health risk to the presence of pesticides in food.
