6 of
8
1.3 Summary
Question
16
.
At a large university, there are 32 males and 660 females in a
statistics class, ﬁnd the probability of selecting 8 males without replacement.
PROBABILITY OF “AT LEAST ONE”
Probability of “At least one”.
Definition 1.6
To ﬁnd the probability of “at least one” of something it is
much
easier
to ﬁnd the probability of
none
, then:
P
(at least one) = 1

P
(none)
(7)
This works because
Compliment of “At least one”.
Definition 1.7
is
none
.
In our statistics class we have 11 females and 7 males, ﬁnd the probability
of randomly selecting
5 students
with:
Question
17
.
At least one female with replacement.
Question
18
.
At least one female without replacement.
1.3
Summary
•
Conditional probability
P
(
B

A
): pay attention and denominator!
•
Independent trials:
P
(
B

A
) =
P
(
B
)
•
Treat sampling without replacement as independent when:
n
N
≤
0
.
05
Anthony Tanbakuchi
MAT167
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7 of
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•
Multiple Trials prob. of
A
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 Spring '11
 Tanbakuchi
 Statistics, Multiplication, Conditional Probability, Probability, United States Senate, Anthony Tanbakuchi

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