Radical Statistics Group: A national network of social scientists in the UK committed to a critique of statistics as used in the policymaking process. The group attempts to build the competence of critical citizens in areas such as health and education. [Radical Statistics Group, 10 Ruskin Avenue, Bradford, UK.]

Radioimmunoassay: An assay performed in clinical and biomedical research laboratories to estimate the concentration of an antigen in a biological specimen. [Clinical Chemistry, 1977, 23, 16247.]

Random: Governed by chance. Not determined completely by other factors. Nondeterministic.

Random allocation: A method for forming treatment and control groups, particularly in the context of a clinical trial. Subjects receive the active treatment or placebo on the basis of the outcome of a chance event, for example tossing a coin. The method provides an impartial procedure for allocation of treatments to individuals, free from personal biases, and ensures a firm footing for the application of significance tests and most of the rest of the statistical methodology likely to be used. Additionally, the method distributes the effects of covariates, both observed and unobserved, in a statistically acceptable fashion. See also block randomization, minimization and biased coin method. [Everitt, B. S. and Pickles, A., 2000, Statistical Aspects of the Design and Analysis of Clinical Trials, Imperial College Press, London.]