Dickerson et al. BMC Public Health 2011, 11:926 http://www.biomedcentral.com/1471-2458/11/926 Page 4 of 10 Figure 1 Effect of independent variables on body mass index by classification. significance (i.e., a = 0.05) were indicated in the legend. Finally, a series of separate calculations was performed to measure the similarity of effect between each BMI classification. An F-statistic was reported along with a p-value to test for similarity, or homogeneity, of effect between classifications. The hypothesis was homo- geneity of effect. Statistical significance of a = 0.05 was used to reject the hypothesis, and indicate heteroge- neity of effect between classifications. Each line graph was assimilated into two quadrant figures for ease of review (please see Figures 1 and 2). Results Sample Employing selection criteria resulted in 1,981 respon- dents in the analytical sample. Table 1 reports the results of the descriptive statistics analysis. Of the respondents, 477 were classified as normal weight, 664 were classified as overweight, 427 were classified as obese class I, 177 were classified as obese class II, and 236 were classified as obese class III. The mean age of the respondents was 59.96, with the youngest respondents belonging to obese class III (54.65 ± 13.61). The majority of respondents were: female, non-Hispanic White, and more than half attended some college. Most respondents also lived in urban areas. On average, the majority of respondents exceeded federal guidelines for weekly minutes of moderate PA. However, nearly a quarter of respondents spent more than 4 h per day watching television. With the exception of rurality, each comparison made between the independent variables and BMI classification was statistically significant at the a = 0.007 level. Since the hypothesis assumes equality between the different BMI classifications for each of the independent variables, a test statistic produ- cing a p-value below the alpha value indicates the hypothesis is rejected and each BMI classification exhi- bits differences to the others on each of the independent variables. This is an appropriate finding as we would expect the BMI classifications to vary on multiple vari- ables. Using an alpha value of 0.007 reflects the tradi- tional use of the 0.05 level of statistical significance adjusted for the multiple comparisons in the statistical test. Dividing 0.05 by the seven comparisons in the test