Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition

Published by McGraw-Hill Education
ISBN 10: 0078136334
ISBN 13: 978-0-07813-633-7

Chapter 4 - Probability and Counting Rules - 4-2 The Addition Rules for Probability - Exercises 4-2 - Page 206: 2


When two events (A, B) are mutually exclusive, we have P(A and B)=0 so the addition rule 2 becomes P(A or B) = P(A)+ P(B) which is the same as addition Rule 1 and can be used for this case.

Work Step by Step

Addition Rule 1: When two events A and B are mutually exclusive, the probability that A or B will occur is P(A or B)= P(A) + P(B) Addition Rule 2: If A and B are not mutually exclusive, then P(A or B) = P(A)+ P(B) - P(A and B)
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