Section 4.2 1 Sampling Theory • sample space set of all possible outcomes of a chance experiment • event set of one or more outcomes from the sample space • probability model method for assigning probabilities to the outcomes in a sample space • disjoint events events which have no outcomes in common, that is, can never occur simultaneously Rules of Probability 1. Probability P(A) of an event A lies between 0 and 1. 2. P(S) = 1 where S is the entire space. 3. P(A does not occur) = 1 – P(A). 4. If A and B are disjoint events, then P(A or B) = P(A) + P(B). Section 4.2 2 Random variables • random variable variable whose value is the outcome of a random phenomenon If there are only finitely many possible outcomes of a random variable, assign probabilities to each of these; then, the probability of any event is the sum of the probabilities of its individual outcomes. If events consist of interval ranges of values of a random variable (like a normally distributed variable) which is described by a certain density curve, the probability of an event is the area under the density curve over that interval.