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Book Problem Set #6
Round all of your final answers to four decimal places if necessary.
#1) A sample survey contacted an SRS of 663 registered voters in Oregon shortly after an
election and asked respondents whether they had voted.
Suppose that p=0.56 (56% of
registered voters actually voted).
We will see in the next chapter that
p
ˆ
~ N(0.56, 0.019).
a) What is the probability that the survey result will be within 4 percentage points of the
truth about the population?
b) What is the probability that the survey result will differ from the truth about the
population by more than 2 percentage points?
#2) Melissa has invested 40% of her funds in Tbills and 60% of her funds in stocks.
If X
is the annual return on Tbills and Y the annual return on stocks, the portfolio rate of
return is:
R= 0.4X + 0.6Y
The returns X and Y are random variables because they vary from year to year:
X= annual return on Tbills
μ
X
= 6
σ
X
= 4.2
Y= annual return on stocks
μ
Y
= 14
σ
Y
= 15
correlation between X and Y
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 Spring '08
 ABDUS,S.

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