Holger von Jouanne-Diedrich hits the casino:
The longest streak in roulette purportedly happened in 1943 in the US when the colour red won 32 consecutive times in a row! A quick calculation shows that the probability of this happening seems to be beyond crazy:
0.5^32[1] 2.328306e-10So, what is going on here? For once streaks and clustering happen quite naturally in random sequences: if you got something like “red, black, red, black, red, black” and so on I would worry if there was any randomness involved at all (read more about this here: Learning Statistics: Randomness is a strange beast). The point is that any sequence that is defined beforehand is as probable as any other (see also my post last week: The Solution to my Viral Coin Tossing Poll). Yet streaks catch our eye, they stick out.
There’s one critical assumption in this post, which is that the game is fair, in that each event has an equal probability of happening. But as a Bayesian, if a roulette table hits red 32 times in a row, it certainly opens the door to the idea that maybe the odds on that table with that dealer aren’t quite equal between red and black.