Two-way ANCOVA was performed to examine the effects of SNPs and gender on the frequency of rescue analgesic administration, the total dose of rescue analgesics administered, and NRS pain scores, incorporating the age, height, and weight of the subjects as covariables. Statistical power analyses for the ANCOVA revealed that the expected power (1 minus type II error probability) was 71% for the Cohen's conventional “medium” effect size 0.25 [29] when the sample size was 129 and type I error probability was set at 0.05. Significant associations were not observed between KCNJ6 G-1250A and the frequency of rescue analgesic administration or total dose of rescue analgesics administered (frequency of rescue analgesic administration: F 2,117 = 1.145, P = 0.322; total dose of rescue analgesics administered: F 2,117 = 1.233, P = 0.295). A significant main effect of KCNJ6 A1032G on the frequency of rescue analgesic administration was observed (F 2,120 = 5.336, P = 0.006). Post hoc analysis revealed significant differences between the A/A and A/G genotypes (P = 0.005) and between the A/A and G/G genotypes (P = 0.010), indicating
