Stat 20: solutions to homework 5
Michael Lugo
October 7, 2010
Chapter 12, # 5
False.
There are two regression lines, one for predicting the wife’s income
from the husband’s income and one for predicting the husband’s income from
the wife’s income.
Chapter 12, # 9
This question describes how we could obtain the regression line for predicting
IQ from parental income. The slope of the regression line is
r
×
SD(IQ)
SD(income)
= 0
.
50
×
15
45
,
000
= 1
/
6
,
000
.
Chapter 13, # 4
The probability that the first card is an ace is 4
/
52. Given this, the probabil
ity that the second card is an ace is 3
/
51, since there are 51 cards remaining
of which 3 are aces.
Similarly, the probabilites that the third and fourth
cards are aces, given that all prior cards are aces, are 2
/
50 and 1
/
49. Finally,
the probability that the fifth card is a king is 4
/
48, since 48 cards remain of
which four are kings. The answer is therefore
4
52
×
3
51
×
2
50
×
1
49
×
4
48
=
96
311875200
=
1
3248700
= 3
.
08
×
10

7
.
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 Spring '08
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 Statistics, Linear Regression, Probability, Regression Analysis, Playing card, Booby prize

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