RICE RATOONING - IRRI books - International Rice Research Institute

ECONOMIC PERSPECTIVES OF RICE RATOONING 25where S i and S j are the standard deviations of profits and B i and B j are the meanlevels of profit (benefits) of crop alternatives i and j.This rule basically helps determine whether the difference in mean profitsbetween treatments is large enough to compensate for the differences in profitvariability.An immediate problem with this model is that statistically defensible estimatesof yield variability may not be available. A working approximation in this case is toestimate (it may be based on expectation) the mean yield (M) and the anticipatedlower (L) and upper (U) yield limits. The standard deviation of this distribution isapproximated byThis rule assumes that yields (and net benefits) are symmetrically distributed.A more general approach, particularly useful when management practices,including ratooning, are being evaluated in multilocation tests, is to plot thecumulative frequency distribution (CDF) of the proposed ratooning practice andthe practice it would replace. The rules of sparse data analysis (1) provide a means ofestimating CDFs from a limited number of points. This approach makes noassumptions about the nature of the underlying distribution function.A hypothetical example of the CDFs of a ratoon rice crop and an alternativecrop are sketched in Figure 3. Three CDFs are displayed. Curve A depicts acropping pattern that includes a ratoon rice crop grown under management system(2)(3)3. Hypothetical cumulative frequency distributions of net returns of threecropping patterns, A, B, and C.