Betting Only on Red
One conceivable strategy would be to bet on the ball landing in a red space for a certain number of spins, for example, 38.
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 2:1,
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. Basically, it is very unlikely for anyone to
spin much more than 18 red spins out of 38 spins.
Betting multiple times
This type of bet is a combination of the red bet and the martingale
system. Except this bet also includes the odd. What you do is you start
off with a bet of 1 on each the red and the odd (or you can do the
black and even). You treat each bet separately. When one bet loses, you
double it. When one bet wins, you set it back to 1. The reason that
this technique keeps you in the game so long is that there is almost a
25% chance of you winning both the red and the odd and there is almost
a 50% chance that you will break even (win one bet and lose the other).
Of course in order for this method to last, you would need an unlimited
source of money. Also, in the long run, because the house still has an
edge, you will lose money just like with all other "unbeatable" casino
games.
Using the dozen bet
There are two versions to this system, single dozen bets and double
dozen bets. In the single dozen bet version, you use a progressively
incrementing stake list starting from the casino table minimum, to the
table maximum. The aim here is to use a single dozen bet to win before
the stake list ends. Many techniques are employed such as: betting on
the same dozen to appear after two consecutive appearances, betting on
the dozen that has appeared most in the last 15, 9, or 5 spins, betting
on the dozen that, after a long absence of 7 or more spins, appears for
the first time. The double dozen bet version uses two dozen bets and
half the stake list size of the single dozen bet version