a statistical principle formulated by Jakob Bernoulli to show a more or less predictable ratio between the number of random trials of an event and its occurrences.

Informal. the principle that, in the long run, probability as naively conceived will operate and influence any one occurrence.

British Dictionary definitions for law of averages

law of averages

noun

(popularly) the expectation that a possible event is bound to occur regularly with a frequency approximating to its probability, as in the (actually false) exampleafter five heads in a row the law of averages makes tails the better bet Compare law of large numbers

The idea that probability will influence all occurrences in the long term, that one will neither win nor lose all of the time. For example, If it rains every day this week, by the law of averages we're bound to get a sunny day soon. This colloquial term is a popular interpretation of a statistical principle, Bernoulli's theorem, formulated in the late 1600s.