A study was conducted to determine whether there is an association between exposure to the organochlorine DDT and breast cancer in women. Blood samples were collected from women diagnosed with breast cancer and healthy control subjects who were matched on age, menopausal status, and date of data collection. From 171 matched pairs, measurements related to DDT (specifically, a byproduct of DDT called DDE) had a mean difference of d = 2.7 ng/ml and standard deviation sd = 15.9 ng/ml. (a) Test the null hypothesis that the mean blood levels of DDE are equal for women with breast cancer and healthy controls. Present a conclusion to address the scientific question. (b) Would you expect a 95% confidence interval for the difference in population means d to contain the value 0. Explain briefly.