To ensure adequate power to detect a significant DRD4 status × intervention status interaction effect given the current sample size, power analyses were conducted based on the results presented in Tables 1 and 2 and Figure 2. The results indicated .86 power to detect a significant two-way interaction effect in the negative binomial model presented in Table 2. Furthermore, on the basis of a method that Luan, Wong, Day, and Wareham (2001) used, the power to detect a significant interaction effect for the model presented in Figure 2 was .93.
