Law of Large Numbers
In probability, the law of large numbers means that the average of the results obtained from a large number of trials should be close to the expected value, and will tend to become closer as more trials are performed. This law is important because it "guarantees" stable long-term results for the averages of some random events. For example, while a casino may lose money in a single spin of the roulette wheel, its earnings will tend towards a predictable percentage over a large number of spins. Any winning streak by a player will eventually be overcome by the law of large numbers that will bring the net gains and losses back to an average.