The mechanism behind a roulette wheel is based on the principles of physics. The wheel is spun in one direction, while the ball is spun in the opposite direction around a track on the outside of the wheel. The ball eventually loses momentum and falls onto the wheel, where it bounces and rolls until it comes to rest in one of the pockets.
The outcome of a roulette spin is determined by the speed of the wheel, the trajectory of the ball, and the location of the deflectors on the wheel. The deflectors are small metal blocks that are located in the area where the ball slows down and comes to rest. They help to randomize the ball’s movement and make it more difficult to predict where it will land. (資料來源)
expected value, in general, the value that is most likely the result of the next repeated trial of a statistical experiment. The probability of all possible outcomes is factored into the calculations for expected value in order to determine the expected outcome in a random trial of an experiment. Expected value uses all possible outcomes and their probabilities of occurring to find the weighted average of the data in the data set. (資料來源)