The Statistical Analysis of Slope-Ratio Assays

SUMMARY: In the past, the statistical analysis of slope-ratio assays has failed to make specific tests of the validity of assumptions essential to the validity of the conclusions to be drawn, and has instead relied upon a composite test of residual variation. The technique introduced in, this paper enables the analysis of variance of assay data to be developed in a manner analogous to that customary for parallel line assays. The paper illustrates the calculations for a 5-point assay, and shows how the analysis of variance, completed with the aid of a set of orthogonal coefficients, gives the required validity tests. Similar analyses for other assay designs, symmetrical and unsymmetrical, are, briefly described, and tables of the orthogonal coefficients for 5-, 7-, 9-, and 11-point designs are given. A final section discusses the need for vatidity tests in biological assays.