31. In a study of the relationship between smoking and serum concentrations of high-density lipoprotein cholesterol (HDL-C) the following data (coded for ease of calculation)

were collected from samples of adult males who were nonsmokers, light smokers, moderate smokers, and heavy smokers. We wish to know if these data provide sufficient evidence to indicate that the four populations differ with respect to mean serum concentration of HDL-C. Let the probability of committing a type I error be .05. If an overall significant difference is found, determine which pairs of individual sample means are significantly different.

Smoking Status Nonsmokers Light Moderate Heavy 12 9 5 3 10 8 4 2 11 5 7 1 13 9 9 5 9 9 5 4 9 10 7 6 12 8 6 2