It is hypothesized that blood levels of lead tend to be higher for children whose parents work in a factory that uses lead in the manufacturing process. Researchers examined lead levels in the blood of 12 children whose parents worked in a battery manufacturing factory and 15 children selected randomly from families where the parents did not work in a factory that used lead. It is assumed that the measurements are independent and come from normal populations. The resulting sample means, and sample standard deviations were:

= 0.015, 1 = 0.004, = 0.006, 2 = 0.006.

(a) Test the hypothesis at level = 0.05

(b) Find a 95% one-sided confidence interval for the difference of the means.