Measures and Mismeasures of Scientific Quality

We present a general Bayesian method for quantifying the statistical reliability of one-dimensional measures of scientific quality based on citation data. Two quality measures used in practice -- ``papers per year'' and ``Hirsch's $h$'' -- are shown to lack the accuracy and precision necessary to be useful. The mean, median and maximum number of citations are on the other hand reliable and permit accurate predictions of future author performance on the basis of as few as 50 publications.