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Chapter 7: Probability
301
Table 7-1:
Table for
Example 7-25
Let
G
= the event of good service
B
= the event of poor service
D
= the event of having a college degree
N
= the event of not having a college degree
(a)
Find
P
(
B
).
Solution:
Recall from Chapter 6 that this is equivalent to the marginal
distribution of the variable
poor service
. Thus
P
(
B
) = 109/200 = 0.545.
(b)
Find
P
(
D
).
Solution:
Again, recall from Chapter 6 that this is equivalent to the
marginal distribution of the variable
college degree
. Thus,
P
(
D
) = 89/200 = 0.445.
(c)
Find
P
(
B
D
).
Solution:
The number of observations in
B
D
is 28. Thus,
P
(
B
D
) = 28/200 = 0.140.
(d)
Find
P
(
B
|
D
).
Solution:
Now,
P
(
B
|
D
) =
P
(
B
D
)/
P
(
D
) = 0.140/0.445 = 0.315. Again,
recall from Chapter 6 that this is equivalent to the conditional distribution of
the variable of
poor service
given the variable of a
college degree
.