You switch on the evening news to hear a headline report of a small new study claiming unforeseen risks to health. The startling nature of the claims is, as so often happens, in inverse proportion to the study's sample size. The news program has already located a group of concerned parents and an apparently off-hand response from health officials. Over the ensuing days, add into the mix other interested parties, a 'maverick' scientist, vitriolic commentary drawing comparisons with thalidomide, and official rebuttals. Before you know it, the attentive population is concerned that the evidence seems to be saying several different things. Now over to you to explain why it doesn't.