Key points are not available for this paper at this time.
is frequently used in agricultural research to express the relationship between the yields of a crop, y, and the amounts of a given fertilizer, x, applied to that crop. This equation is slightly different to that used by Stevens (1951) in that a negative sign is given to the term Opx. This change allows y to increase with positive values of A. Stevens (1951) has described an efficient method for determining the parameters a, ,3 and p. He provided tables for 5, 6 anid 7 equally spaced ordinates which considerably reduce the arithmetic labour of his method and which have the valuable feature that they enable the variances and covariances of the estimates of a, ,3 and p to be directly determined. These tables have been extended by S. Lipton on the electronic computer at Rothamsted to cover the range of n = 3 to n = 12. Since Stevens' method is one of successive approximation, it is admirably suited for use on the electronic computer. Pimentel Gomes (1953) has shown that, with equally spaced ordinates, efficient estimates of p can be obtained by solving equations of the type
H. D. Patterson (Sat,) studied this question.