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Abstract:
A recent experience as an expert witness in a legal action intended to prevent the fluoridation of water supplies has emphasized to me some of the problems of explaining statistical reasoning to persons unfamiliar with the mode of thought. The procedures of cross-examination are not ideal for clarifying scientific truth, and regrettably the language of statistics offers much scope for misunderstanding when words used technically are read with more colloquial meaning. I illustrate this by discussing the meaning of significance tests and by examples relating to the combination of independent test results, the misunderstanding of independence, covariance analysis, the use of interpolation, the relation between source of data and interpretation, and spurious correlation.