Roulette: Betting strategies and tactics: Betting only on red

There are 18 red spaces on a roulette table with 38 total spaces. Dividing 18 by 38 yields a probability of landing on red of 47.37%. This probability can be used in a binomial distribution and made into an approximate standard normal distribution.

Doing so indicates that, if one were to spin the wheel 38 times, there is a 99% probability that the ball would land on red at least 10 times. There is an 83% probability that in 38 spins, the ball will land on red at least 15 times. Out of 38 spins, there's a 50% chance that 18 will be red.

However, the break-even point is 19 spins, since the bet on red is 1:1, and the probability of 19 red spins in 38 is only 37%. This indicates the difficulty of winning by only betting on red.

The results occur because, as indicated by the 18 divided by 38 equals 47.37% figure, the ball will land on red less than half the time. This percentage applied in the binomial and standard normal distributions creates the vast divide in probability from 18 red spins to 19 red spins out of 38 spins. It is very unlikely for anyone to spin much more than 18 red spins out of 38 spins.

From Wikipedia's

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