How does one calculate the probability that an event does not happen?
The probability of an event not happening is 1 minus the probability that the event will happen. Mathematically, the equation looks like this: Pr(not_A) = 1 – Pr(A) Example: What is the probability of not drawing a face card from a single deck of cards? Pr(no face card) = 1 – Pr(face card) Step one is to determine the number of face cards in a single deck. Because the number of face cards in a single deck is 12, N(face card) = 12. Step two is to determine the total number of cards in a single deck Because the total number of cards in a single deck is 52, s = 52. Step three is to divide N(face card) by s, so Pr(face card) = N(face card)/s = 12/52 = 0.230769 Step four is to subtract Pr(face card) from 1, so Pr(no face card) = 1 – 0.230769 = 0.769231 Therefore, the probability of not drawing a face card from a single deck is 0.769231. This means there is almost a 77% chance of not drawing a face card from a single deck of cards.
