This function calculate the treatment efficacy according to the Henderson and Tilton formula (1955). #' For non-uniform populations, the Henderson and Tilton (1955) formula is suited which allows us to judge differences in the population development. In this formula the mortality ratio is corrected on the control mortality Eff = (1 - (T_a * C_b) / (T_b * C_a)) * 100 with : Tb number of mites before treatment Ta number of mites after treatment Cb number of mites before treatment in the check plot (TNT) Ca number of mites after treatment in the check plot (TNT) Efficacy is expressed in percentage.
Reference : Henderson, C.F. and E. W. Tilton. 1955. Tests with acaricides against the brow wheat mite, J. Econ. Entomol. 48:157-161. See also : Abbott (1925) formula