ABSTRACT
This chapter introduces the key concept of probability its fundamental rules and properties, and discusses most basic methods of computing probabilities of various events. The concept of probability perfectly agrees with our intuition. In everyday life, probability of an event is understood as a chance that this event will happen. It is often easier to compute probability of an intersection than probability of a union. Probabilities arise when one considers and weighs possible results of some experiment. Some results are more likely than others. An experiment may be as simple as a coin toss, or as complex as starting a new business. A collection of all elementary results, or outcomes outcome of an experiment, is called a sample space. Any set of outcomes is an event. Thus, events are subsets of the sample space. For combinations with replacement, the order is not important, and each object may be sampled more than once.
