What you’ll learn to do: Calculate conditional probabilities and probabilities of complementary evens

What is the chance of a strong storm or a tornado on a given day?  If you have wondered about the answer to this question, you are thinking about the concepts of probability.  Probability describes how likely a particular outcome is. Probabilities can range from 0 (the event will never happen) to 1 (the event is guaranteed to happen). Before we look at rules involving probability, we need to be familiar with basic terminology about probability.