How does one calculate the probability of an event?
In order to determine the probability of an event A, Pr(A), we need to count the number of outcomes corresponding to event A. Let’s call this value N(A). Then we need to divide N(A) by the total number of possible outcomes. Let’s call the total number of possible outcomes ‘s’. Mathematically, the equation looks like this: Pr(A) = N(A)/s Example: What is the probability of drawing a red card from a single deck of cards? Step one is to determine the number of red cards in a single deck. Because the number of red cards in a single deck is 26, N(A) = 26. 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(A) by s, so Pr(A) = N(A)/s = 26/52 = 0.5 Therefore, the probability of drawing a red card from a single deck is 0.5. This mean s there is a 50% chance of drawing a red card from a single deck of cards.
