Statistical Analysis of Random Sample Surveys in the 2008 Presidential Election - Prof. Du, Quizzes of Statistics

Download Statistical Analysis of Random Sample Surveys in the 2008 Presidential Election - Prof. Du and more Quizzes Statistics in PDF only on Docsity! Stat 113 Quiz 12 A key (10 points in total) Jun 05, 2009 Presidential Election 2008 The following questions are all concerned about a random sample survey of 500 registered voters all across the country, which was conducted shortly before the 2008 presidential election. It was observed that 275 of voters were for Obama in this survey. Now assuming only random sampling error exists in this survey. Usually, p, the proportion of nationwide popular vote for Obama is a parameter of political interest. Q1. How much is the sample proportion for Obama in this sample survey? (1 point) 275/500 = 0.55 How much is the margin of error in this sample survey? (Round to 3 decimals) (1 point) 1.96*sqrt(0.55*0.45/500) = 0.022 What is the 95% confidence interval for the p? (1 point) (0.528, 0.572) Q2. A political analyst predicted that Obama would win more than 6% of popular votes. To verify this, you decide to run a Z test. Write down the two hypotheses statement about p. (2 points) H0: p = 53% vs Ha: p > 53% How much is the test score of your Z test? (2 points) (0.55-0.53)/sqrt(0.53*0.47/500) = 0.90 How much is the p-value of your Z test? (2 points) P(Z>0.90) = 0.184 At significance level 0.05, what is your conclusion? (1 point) Do not reject H0