This chapter provides an explanation of probability for processes with a finite number of possible outcomes. It explains the meaning of probability, as well as how to calculate probability and odds. It also examines the relationship between complementary events.

The first section deals with the probability of a single event. It provides an equation for probability which you will use to calculate the probabilities of various events.

The second section introduces the concept of complementary events--that is, events whose probabilities add up to 1. When two events are complementary, one occurs if and only if the other does not. This second also discusses the notion of odds and their relation to probability.

People use probability and odds in many situations -- to decide what kind of weather to prepare for, whether or not to buy a stock, and how much to bet when gambling. Probability helps people understand which choices are safe and which choices are risky. Of course, this task is much easier when we have fluent knowledge of probability. By learning about probability, we can learn about the likelihood of future events, and prepare accordingly.