The accompanying data on milk volume (in grams per day) were taken from the paper “Smoking During Pregnancy and Lactation and Its Effects on Breast Milk Volume” (American Journal of Clinical Nutrition [1991]: 1011– 1016):

Smoking 621 793 593 545 753 655 mothers 895 767 714 598 693 Nonsmoking 947 945 1086 1202 973 981 mothers 930 745 903 899 961 Compare and contrast the two samples