Variationa Sum of squares Degree of freedom Mean sum of squares F-ratio p value ‘Within’ 17.07227 28 0.609724     ‘Between’ 6.553769 3 2.18459 3.5829 0.026 Class type 1 2.888233 1 2.888233 4.7370 0.038 Class type 2 0.28282 1 0.28282 0.4638 0.501

aVariance of the data set is divided into two parts, i.e. within group variance and between group variance. The between group variance is composed of three subparts,including variation caused by obesity (Class type 1), cigarette smoke (Class type 2), and the synergy between these two factors (Interaction).

Table 3: Two way ANOVA table for GPC/PC ratio.