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® The following methods are used to check the validity of statements: direct method contrapositive method (iii) method of contradiction (iv) using a counter example. Historical Note The first treatise on logic was written by Aristotle ( B.C.- B.C.). It was a collection of rules for deductive reasoning which would serve as a basis for the study of every branch of knowledge. Later, in the seventeenth century, German mathematician G.

W. Leibnitz ( – ) conceived the idea of using symbols in logic to mechanise the process of deductive reasoning. His idea was realised in the nineteenth century by the English mathematician George Boole ( – ) and Augustus De Morgan ( – ) , who founded the modern subject of symbolic logic. v “Statistics may be rightly called the science of averages and their