At a time in U.S. history when there appears to be genuine concern about the number of illegal aliens living in the United States, there also appears to be concern over the number of legal immigrants allowed to move to the United States. In a recent poll that included questions about both legal and illegal immigrants to the United States, 51% of the n = 900 registered voters interviewed indicated that the U.S. should decrease the number of legal immigrants entering the United States.

a. What is a point estimate for the proportion of U.S. registered voters who feel that the United States should decrease the number of legal immigrants entering the United States? Calculate the margin of error.

b. The poll reports a margin of error of ± 3%. How was the reported margin of error calculated so that it can be applied to all of the questions in the survey?