The Addition Rule
The addition rule in probability explains the probability of one or more of several events occurring. I will start by showing the probability of two events. We can consider the probability of either event A or event B occurring when they are both mutually exclusive events.
Suppose we roll one die again. This time we are interested in two events. Event A is that the die will come up with an odd number. Event B is that the die will come up with an even number. Event A is satisfied if there is a 1, 3, or 5. Event B is satisfied if there is a 2, 4, or 6.
The probability we are interested in is the probability that either event A or event B will occur. This means that if the die comes up with a 1, 2, 3, 4, 5, or 6 we will meet the ...