CH. 4
Class examples
I
.
Consider the discrete probability distribution when answering the following question.
X
1
2
4
6
8
P (x)
.
20
?
.
30
.
10
.3
o
Find the probability that
X is large than 2.
o
Calculate the
mean
and
variance
for this distribution.
o
Find the probability that
X is at most 4.
o
Find the probability that
µ  σ < X < µ +
σ.
II
.
Current estimates suggest that only 60% of the homebased computers have access to online
services. Suppose 20 people with homebased PC were randomly and independently sampled.
•
Find the probability that
at least 10 but at most 14
currently have access to online services.
•
Find the probability that
fewer than quarter
of those sampled currently have
no
access to online
services.
•
Find the probability that
at least 18
currently have access to online services.
•
How many
people do you expect currently
do not
have access
to online services?
III.
According to a recent study, 1 in every 10 women has been a victim of domestic abuse at some
point in their lives. Suppose we have randomly and independently sampled 20 women and
asked whether they have been a victim of domestic abuse at some point in their lives.
Find the probability that
at most 6
of the sampled women have been the victim of domestic abuse at
some point in their lives.
Find the probability that
less
than 15
of the sampled women
have not
been the victim of domestic
abuse at some point in their lives.
How many
of the 20 women do we expect
have been the victim
of domestic abuse?
IV
. Current estimates suggest that only 45% of the homebased computers have access to online services.
Suppose 25 people with homebased computers were randomly and independently sampled. Find the
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 Fall '08
 STAFF
 Probability, Variance, online services

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