Let’s start with the easy part: Many events have known probabilities. The probability of flipping heads with a fair coin is ½. The probability of rolling a one with a single die is . Other events have probabilities that can be inferred on the basis of past data. The probability of successfully kicking the extra point after touchdown in professional football is .94, meaning that kickers make, on average, 94 out of every 100 extra-point attempts.
