In 2008, a Gallup Poll asked 2336 U.S. adults aged 18 or over how they rated economic conditions. In a poll conducted from January 27 through February 1, 2008, 24% rated the economy as “Excellent/Good.” A recent media outlet claimed that the percentage of Americans who felt the economy was in “Excellent/Good” shape was, in fact, 28%. Does the Gallup Poll support this claim?

a) Find a 95% confidence interval for the sample proportion of U.S. adults who rated the economy as “Excellent/ Good.” Check conditions.

b) Does your confidence interval provide evidence to support the claim?

c) What is the significance level of the test in part (b)? Explain.