In view of the low frequency of the 16p11.2 deletions, all reported statistical tests were carried out using Fisher’s exact test29. This was applied to comparisons of separately-ascertained cohorts or categories and was carried out on contingency tables constructed for the number of subjects carrying/lacking a 16p11.2 deletion (zero or one copies, as no homozygous deletions were observed) versus the obesity status/ascertainment of the individual. Since no homozygous deletions were observed, it was unnecessary to make a prior distinction between recessive, additive and dominant models of disease risk. For overall analysis of the obesity risk resulting from a deletion, cohorts were pooled according to their obesity status determined according to the criteria described above, and the described tests were then applied to the pooled data. Odds ratios and 95% confidence limits were calculated as described30.
