Unformatted text preview: CH 4: Basic Probability 1. Basic Concepts (A) Sample Space: The collection of all possible outcomes. (B) An Event: An event is a subset (part) of the sample space in which you are interested.
(C) Probability: number of ways in which the event occurs . . X
Probability _ total number of pouible outcomes - 7f" (eq4.1) EX] Note 1: The probability of an event is a number between 0 and 1.
Note 2: The probability of the sample space is l. (D) Some basic set notations and formulas. (l) The complement of an event A, denoted by A’ (or A) is the set of all outcomes that
are not in A. And the complement of A has probability P(A’) u 1 - P(A) (2) The union of two events A, B, denoted by (A or B), is the set of all outcomes that
are in A, B or both. (3) The intersection of two events A, B, denoted by (A and B), is the set of all outcomes
that are in A and B. Note: P(A and B) is the joint probability. (4) If the intersection (A and B) is empty (i.e. PM and B) = 0), then the two events
A, B are called mutually exclusive (disjoint). (5) The marginal probability
pm) = PM and 3,) + PM and 3,) + - -- + PM and 31:) («14-2) where 3;, Ba, - - - B1. are k mutually exclusive and collectively exhaustive (one of the
events must occur). (6) The general addition rule:
PM or B) = PM) + P(B) - PM and B). (eq4.3) ...
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- Spring '11