ABSTRACT
In today’s society the use of chemicals, i.e., insecticides for insect control, drugs to treat illness, and fertilizer for crop control, is widespread. With so many chemical entities in our environment, a point of mutual concern to everyone involves the interaction of these chemicals. That is, we are interested in understanding the effects due to using these chemicals in combination. The effects could be both positive and negative. An example of a positive effect would be if two insecticides were used in combination to produce better insect control than that produced when either ingredient was used singly. A negative effect would result if a physician administered two drugs to patients and the toxic effect of the combination was greater than when either drug was used by itself. In that same view, it could also be that when two drugs are used in combination the effectiveness of the combination is either less than or greater than the effectiveness of either drug used singly.
