In both modalities and all locations, differences between males and female became statistically significant by age 16 and continued to age 25. Effect sizes of gender difference when significant range from 0.1 to 0.6. From age 16 onward p-values for age specific gender differences ranged from p < 4 × 10−4 to p < 10−15. Gender differences in the amount of decrease of the mean values from age 12 to age 25 were significant when evaluated over all 6 modality/location variables, obtained from bootstrapping. (See Table 1 for the values of the decreases.) It should be emphasized that there is considerable overlap between the distributions of power values for males and females. The large sample size implies that differences between the means of males and females can be quite significant without being large in terms of the variance within the groups.
