The information gathered from opinion polls and political surveys is becoming so
ID: 3135437 • Letter: T
Question
The information gathered from opinion polls and political surveys is becoming so increasingly important for candidates on the campaign trail that it is hard to imagine an election that lacks extensive polling. An NBC NewsIWall Street Journal survey (August 5-9. 2010) of 1.000 adults asked people's preferences on candidates and issues prior to the midterm 2010 elections. Some of the responses to the survey are shown below, as well as responses from prior surveys. In general, do you approve or disapprove of the way Barack Obama is handling the aftermath of the Gulf Coast oil spill in August 2010 (and George W. Bush's handling of Katrina in March 2006)? Which are more important to you in your vote for Congress this November: domestic issues such as the economy, health care, and immigration: or international issues such as Afghanistan, Iran, and terrorism? In a report, construct 95% confidence intervals for the relevant population proportions to: Compare the approval rates of President Obama's handling of the Gulf Coast oil spill and President George W. Bush's handling of the Hurricane Katrina crisis. Compare the importance of domestic issues in August 2010 and in September 2006.Explanation / Answer
1) SE(AO-AW)=sqrt [(pAO qAO)/n AO+(p AW qA)/n AW]=sqrt [(0.50*0.50)/500+(0.36*0.64)/360]=0.034
ME=zcritical*SE(AO-AW)=1.96*0.034=0.067
The 95% c.i=(0.50-0.36)+-0.067=0.14+-0.067=0.073 to 0.207 [Note, AO and AW stands for approval Obama and Approval Georege W Bush].
2. The 95% c.i=(0.73-0.43)+-ME=0.30+-(0.03*1.96)=0.24 to 0.36
ME=zcritical*SE(D10-D6)=1.96*0.03=0.06
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