Chapter 15

# Chapter 15 - Chapter 15 Read: Probability Rules ActivStats:...

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Chapter 15 Probability Rules ActivStats: 15 Read: Chapter 15 Model of a random phenomenon 1. The sample space S (or ) = the set of all possible outcomes 2. Events = subsets of the sample space A c = "A does not occurs" - the complement of A Two events are called disjoint , if they cannot occur simultaneously Combined events: A or B, A and B 3. Probability = a function that to each event A assigns a number P(A) 0 P(A) 1 P(S) = 1 P(A c ) = 1-P(A) if A are B are disjoint , then P(A or B) = P(A) + P(B) Example (Model with Equally Likely Outcomes) If the sample space has k possible outcomes and all are equally likely, then each has the probability 1/k and the probability of an event A is outcomes possioble all of count A in outcomes of count A P = ) ( Most of models do not have this property.

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Addition Rule for disjoint events: P(A or B) = P(A) + P(B) On Venn diagram the probability behaves as area . General addition rule P(A or B) = P(A) + P(B) - P(A and B) Example:
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## This note was uploaded on 07/25/2008 for the course STT 200 taught by Professor Dikong during the Summer '08 term at Michigan State University.

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Chapter 15 - Chapter 15 Read: Probability Rules ActivStats:...

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