Answers to special review exercises for midterm 2
Michael Lugo
November 1, 2010
15.18(a)
There are two ways that this can happen 
A
2
,B
5 or
A
5
,B
2. There are 30
possible outcomes, all equally likely. The answer is 2
/
30 = 1
/
15.
15.18(b)
A sum of 7 can occur as
A
1
,B
6;
A
2
,B
5;
A
3
,B
4;
A
4
,B
3;
A
5
,B
2. Thus 5 out
of the 30 possible equally likely outcomes have sum 7; the answer is 5
/
30 = 1
/
6.
15.18(c)
One number is bigger than twice the other if the numbers are
•
A1, with B3, B4, B5 or B6;
•
A2, with B5 or B6;
•
A3, with B1;
•
A4, with B1;
•
A5, with B1 or B2.
So there are 10 total outcomes where one number is bigger than twice the other,out of
30; the answer is 10
/
30 = 1
/
3.
15.19(a)
This is (39
/
52)
×
(38
/
51)
×
(37
/
50)
×
(13
/
49)
≈
0
.
110. The factors of the
product are conditional probabilities.
15.19(b)
There are 49 cards left, of which 13 are hearts; the answer is 13
/
49.
15.20
±
10
3
²±
1
2
²
10
=
10
×
9
×
8
3
×
2
×
1
±
1
2
²
10
=
120
1024
=
15
128
≈
0
.
117
23.11(a)
This description describes the process of ﬁnding the regression line for predict
ing the income of the wife from the income of the husband. The regression line has slope
r
×
SD
(
y
)
/SD
(
x
) =
.
33
×
30000
/
40000
≈
0
.
25.
23.11(b)
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 Spring '08
 Staff
 Statistics, Normal Distribution, Probability, Standard Deviation, Standard Error, regression line, blue marbles

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