Question: Birthweight of an infant has been hypothesized to be associated with smoking status of the mother during first trimester of pregnancy. This hypothesis is tested by recording birthweights of infants and smoking status of mother during pregnancy for all mothers who register at the prenatal clinic at a particular hospital within a 1-month period. The mothers are divided into four groups according to smoking habit, and the sample of birthweights in pounds within each group is as follows:

Group 1: Mother is nonsmoker (NON):

7.5 6.2 6.9 7.4 9.2 8.3 7.6

Group 2: Mother is ex-smoker (smoked at some time before pregnancy but not during pregnancy) (EX):

5.8 7.3 8.2 7.1 7.8

Group 3: Mother is current smoker and smokes less than 1 pack per day (CUR<1)

5.9 6.2 5.8 4.7 8.3 7.2 6.2

Group 4: Mother is current smoker and smokes 1 pack per day or more (CUR \[\ge \] 1):

6.2 6.8 5.7 4.9 6.2 7.1 5.8 5.4

a. Are the mean birthweights different overall in the four groups?

b. Test for all differences between each pair of groups, and summarize your results using the LSD procedure (Least significant difference)

c. Perform the same tests in problem b using the method of multiple comparisons. (use Bonferroni).