Addition Rule
Section 3.3
Summer 2013 - Math 1040
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Roadmap
§3.3 p 156 - 160
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Venn Diagrams
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Set intersection and union.
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The addition rule.
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Venn Diagram
A : iPad owner, B : Kindle
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Venn Diagram
Mutually exclusive events.
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Venn Diagram
Three events.
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Intersection and Union
The intersection of two events are the outcomes that are in common. We
know this as the event A and B.
The union of two events are all outcomes in both of them together. We
know this as the event A or B. This is ’inclusive,’ meaning it could come
from events A, B, or both.
When two events have nothing in common, it is said these events are
mutually exclusive. Meaning the event A or B is, ’empty.’
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The Addition Rule
The union of events A or B occurs with probability,
P(A or B) = P(A) + P(B) − P(A and B).
When the events are mutually exclusive, P(A and B) = 0. The addition
rule simplifies in this case to
P(A or B) = P(A) + P(B).
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Venn Diagram
A : iPad owner, B : Kindle
A or B is the event the owner has an iPad or a Kindle.
A and B is the event the owner has an iPad and a Kindle.
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Assignments
Assignment:
1. In class examples.
2. Page 161, 1 - 25 odd, 29
Vocabulary: mutually exclusive events, the addition rule
Understand: Find probabilities of two events. The summary of probability
rules so far include definition of theoretical and statistical probability,
probabilityies range between 0 and 1, probability of complementary events,
the multiplication rule and addition rule.
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