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Chapter 5
Contingency Table
FR
SO
JR
SR
M
xxxx
F
Different kinds of probabilities
• marginal – P(F), P(JR), .
..
• joint – P(F and SR), .
..
• OR’s – P(F or SR), .
..
• conditional – P(SR  F),.
..
• complement –
,...
PSR
()
Important terms: 1) independent
³
events that don’t affect each other
2) mutually exclusive
³
events that cannot both occur
Two Rules
1) P(A or B) = P(A) + P(B) provided A and B are mutually exclusive
2) P(A and B) = P(A) · P(B) provided A and B are independent
NOTE
: Both rules apply to two or more
events
Sections 5.3 and 5.4
 Word problems
Put these into a 2 x 2 contingency table
A
A
Total
B1
21
8
3
0
B
86
2
7
0
Total
20
80
100
You are always given three pieces of information, such as:
P(A) = .2, P(B) = .3, and P(BA) = .6
³
This leads to the values in the above table.
NOTE
: Sometimes the third piece of information is P(A and B).
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View Full DocumentChapter 6
Section 6.1
What is a discrete random variable?
X = (counting something)
Representing a discrete random variable
1. Make a list
0 with probability ___
1 with probability ___
X =
2 with probability ___
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 Fall '11
 Pavur

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