An October 2011 CBS News Poll on illegal immigrants interviewed 1012 randomly se
ID: 3255763 • Letter: A
Question
An October 2011 CBS News Poll on illegal immigrants interviewed 1012 randomly selected American adults. Of those in the sample, 688 said that they “oppose allowing the children of illegal immigrants to attend state college at the lower tuition rate of state residents.” Although the samples in national polls are not SRSs, they are similar enough that our method gives approximately correct confidence intervals. Explain what the parameter p is in this setting.
A. Select the correct choice below.
a. The proportion of all U.S. adults who took part in this poll.
b. p is the proportion of all American adults who agree with allowing the children of illegal immigrants to attend state college at the lower tuition rate of state residents.
c. p is the proportion of all American adults who oppose allowing the children of illegal immigrants to attend state college at the lower tuition rate of state residents.
B: Fill in the blanks:
The 95 percent confidence interval for the population proportion p is from ______ to _____. (Give your answers to three decimal places.) Answer 1 113 Answer 2
C: Which of the following statements is true?
a. The estimated margin of error is plus or minus one percentage point for this poll result.
b. The interval is based on a method that includes the true population proportion p about 95 percent of the time.
c. Based on a procedure that gives correct results 95 percent of the time, we believe that the sample result is within 0.027 of the population proportion.
Explanation / Answer
A. Select the correct choice below.
Answer:
c. p is the proportion of all American adults who oppose allowing the children of illegal immigrants to attend state college at the lower tuition rate of state residents.
B: Fill in the blanks:
Answer:
n=1012
p=688/1012=.679842
95%confidence interval is given by
(p-1.96*sqrt(p*(1-p)/n),p+1.96*sqrt(p*(1-p)/n)) #sqrt means square root
=(0.651098,0.708586)=(0.651,0.709) (upto 3 decimal places)
C: Which of the following statements is true?
Answer:
b. The interval is based on a method that includes the true population proportion p about 95 percent of the time.
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