2014 In March 2014, Barack Obama's approval rating stood at 40% in Gallup's daily tracking poll of 1500 randomly surveyed U.S. adults, (www.gallup.com /poll/113980/gallup-daily-obama-job-approval.aspx)
a) Make a 95% confidence interval for his approval rating by all U.S. adults.
b) Based on the confidence interval, test the null hypothesis that Obama's approval rating was no worse than his November 2011 approval rating of 45%.