Immigration reform has focused on dividing illegal immigrants into two groups: long-term and short-term. In a random sample of 958 construction workers from the Northeast, 66 are illegal short-term immigrants. In the Midwest, 42 out of a sample of 1070 are illegal short-term immigrants.
a) Is there evidence that the percentage of construction workers who are illegal short-term immigrants differs in the two regions?
b) Give a 90% confidence interval for the difference in proportions.