Law of large numbers

Definition and stakes

Portrait of William Petty William Petty The Economic Writings of Sir William Petty… (1899)

In other words he pursued the method of political arithmetic as distinguished from statistics. Statistics demands enumeration. The validity of its inferences depends upon the theory of probabilities as expressed in the Law of Large Numbers. Therefore it adds, it does not multiply. Political arithmetic, as exemplified by Petty, multiplies freely; and the value of its results varies according to the nature of the terms multiplied. For example, in the absence of a census Petty had to calculate the population of London, of England, and of Ireland.
Source: Wikisource

John Venn The Logic of Chance, 3rd edition

Hence, if the statistics are large enough to be satisfactory, there has been some influence at work which has improved the chances of mere coincidence in the ratio of 20 to 1. We are in fact so little able to realise the meaning of very large numbers,—that is, to retain the ratios in the mind, where large numbers are concerned,—that unless we repeatedly check ourselves by arithmetical considerations we are too apt to treat and estimate all beyond certain limits as equally vast and vague.
Source: Gutenberg

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