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STAT 400
Examples for 01/24/2011
Spring 2011
1.
The probability that a randomly selected student at Anytown College owns
a bicycle is 0.55, the probability that a student owns a car is 0.30, and the
probability that a student owns both is 0.10.
P( B ) = 0.55,
P( C ) = 0.30,
P( B
∩
C ) = 0.10.
a)
What is the probability that
a student selected at random
does not own a bicycle?
P( B
'
) = 1 – P( B ) = 1 – 0.55 =
0.45
.
C
C
'
B
0.10
0.45
0.55
B
'
0.20
0.25
0.45
0.30
0.70
1.00
b)
What is the probability that a student selected at random owns either a car or
a bicycle, or both?
P( B
∪
C ) = P( B ) + P ( C ) – P( B
∩
C ) = 0.55 + 0.30 – 0.10 =
0.75
.
OR
P( B
∪
C ) = P( B
∩
C ) + P( B
'
∩
C ) + P( B
∩
C
'
) = 0.10 + 0.20 + 0.45 =
0.75
.
OR
P( B
∪
C ) = 1 – P( B
'
∩
C
'
) = 1 – 0.25 =
0.75
.
c)
What is the probability that a student selected at random has neither a car nor
a bicycle?
P( B
'
∩
C
'
) =
0.25
.
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View Full Document 2.
During the first week of the semester, 80% of customers at a local convenience
store bought either beer or potato chips (or both).
60% bought potato chips.
30% of the customers bought both beer and potato chips.
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This note was uploaded on 02/24/2011 for the course STAT 400 taught by Professor Kim during the Spring '08 term at University of Illinois, Urbana Champaign.
 Spring '08
 Kim
 Probability

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