SUMMARY Answers to questions concerning adequate sample size in a one-way analysis of variance situation depend on such things as the number of categories to be compared, the levels of risk an experimenter is willing to assume and some knowledge of the noncentrality parameter. The accompanying tables which provide answers without need of iteration are for the experimenter who can deal better intuitively with an estimate of the standardized range of the means than with the noncentrality parameter. Maximum values of the standardized range, r, are tabulated when the means of k groups, each containing N observations, are being compared at a and /8 levels of risk, for ac = 0-01, 0.05, 0O1, 0-2; /3 = 0-005, 0-01, 0 05, 0-1, 0-2, 0-3; k = 2 (1) 6; N = 2 (1) 8 (2) 30, 40, 60, 80, 100, 200, 500, 1000.