Labor force. Immigration reform has focused on divid- ing illegal immigrants into two groups: long-term and short-term. According to a recent report, short-term unau- thorized workers make up nearly 6% of the U.S. labor force in construction (Pew Hispanic Center Fact Sheet, April 13, 2006). The regions of the country with the lowest percentage of unauthorized short-term immigrant con- struction workers are the Northeast and the Midwest. 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.