ABSTRACT
It is the all-important factor in the minimal regions, where the average or normal rainfall is generally necessary for successful crop production. This version, based on the mean deviation as a percentage of the average, is exceedingly generalized, to the point where, except for very broad contrasts, it is more misleading than helpful. This is, in fact, the basis of the probability estimates which will be discussed later. Despite this, it is still often argued that percentage variability varies inversely with the mean rainfall. For example, in the Atlas of Uganda it is suggested that the concept provides a better basis than does the mean annual rainfall for planning and development projects in agriculture, forestry, hydrology, roadmaking and such matters. It must be remembered that all these percentage probabilities are theoretically related to an infinitely large population, so that there is no necessary reason for them to apply in detail within any shorter, finite period.
