Dickerson et al. BMC Public Health 2011, 11:926 http://www.biomedcentral.com/1471-2458/11/926 Page 5 of 10 Figure 2 Effect of independent variables on body mass index by classification, continued. results in a more stringent threshold of 0.007. This ensures maximum confidence when rejecting the hypothesis. Simultaneous quantile regression–overall model results Table 2 reports the results of the simultaneous quantile regression model. Results are reported by BMI classifica- tion. For those of normal weight, respondents were more likely to be older, female, and self-report as Hispa- nic. For those classified as overweight, respondents were more likely to be older, female, self-report as non-His- panic White, African-American or Hispanic, live in a rural location, and spend more hours per day watching television. For those classified as obese class I, respon- dents were more likely to be younger, self-report as non-Hispanic White, African-American or Hispanic, to have attained less education, spend more hours per day watching television, and spend fewer minutes per week engaged in moderate PA. For those classified as obese class II, respondents were more likely to be younger, self-report as African-American, to have attained less education, to spend fewer minutes per week engaged in moderate PA, and spend more hours per day watching television. Finally, for those classified as obese class III, respondents were more likely to be younger, female, self-report as African-American, to have attained less education, to spend fewer minutes per week engaged in moderate PA, and spend more hours per day watching television. These results indicate a general pattern of PA and sedentary behavior coefficients becoming more important in determining BMI as the BMI classification increases. For example, the coefficient for the PA vari- able among those who are in the obese class I BMI clas- sification is -0.0010 for each minute per week of moderate PA. This means that all things being equal, as more minutes per week of moderate PA are performed, BMI is reduced by the coefficient value. However, for those in the obese class II and III BMI classifications, the coefficient for minutes per week of moderate PA is -0.0020, a 100% increase in the effect of this variable on BMI. Hence, we can use the statistically significant coef- ficients to begin identifying relationships between vari- ables of PA, sedentary behavior, and BMI according to BMI classification.