Chapter 12, Problem 7 See text.

Sample	n	x-bar	s
Nonsmokers	269	115	13.4
Current smokers	53	114	10.1
Ex-smokers	28	118	11.6
Tobacco chewers	9	126	12.2

a. Calculate the estimate of the within-groups variance. b. Calculate the estimate of the between-groups variance. c. At the 0.05 level of significance, test the null hypothesis that the mean systolic blood pressures of the four groups are identical. What do you conclude? d. If you find that the population means are not all equal, use the Bonferroni correction to determine where the differences lie. What is the significance level of each test?