Since 1935, the Gallup organization – best known for the Gallup Poll – has been a leader in the measurement and analysis of people’s attitudes, opinions, and behavior. In a September 2003 survey, 1,200 registered voters were interviewed and asked: “California is facing a record 38-billion deficit. Do you think California should or should not raise sales taxes to reduce the state budget deficit?” Among those polled, 498 indicated they were in favor of raising sales taxes.
a. Compute a 99% confidence interval for the estimate of the proportion of voters who were in favor of raising sales taxes. Indicate both low-end and high-end estimates.
b. A smaller sample of 700 voters identified themselves as independent. Among the independent voters, 364 said they would support higher sales taxes. The survey cited a margin of sampling error of no more than 5 percentage points. Is this claim correct? Use the same confidence level as in part a.