law of averages

Noun

law of averages

1. The statistical tendency toward a fixed proportion in the results when an experiment is repeated a large number of times.
   • Near-synonym: law of large numbers (not always differentiated)
   • ... as they will not have sufficient distribution of risk to permit the law of averages to play its part and a severe total loss may ...1919, William David Winter, Marine Insurance: Its Principles and Practice, McGraw-Hill, page 96

   Synonyms:

   law of large numbers

2. (informal) An imaginary or perceived "law" of probabilities which is wrongly used to predict results in the short-term.
   • This coin has landed on heads ten times, so by the law of averages it must land on tails next time.
   • In the nature of things a good many somebodies are always in hospital, and the law of averages had picked on me to be one of them a week or so before. It might just as easily have been the week before that - in which case I'd not be writing now: I'd not be here at all.1951, John Wyndham, The Day of the Triffids, Harmondsworth: Penguin Books, published 1954, page 7
3. A real or purported law from centuries past regarding the distribution of recompense after a loss at sea due to an act of God, said by some (but not others) to explain why the word average evolved a sense having to do with means, medians, modes, etc.