This is an interesting study that addresses your distribution points directly. > 3233 young and old adolescents representative of the population > For the you

This is an interesting study that addresses your distribution points directly. > 3233 young and old adolescents representative of the population > For the young adolescents, the observed difference in Mechanical Reasoning is equivalent to 10 IQ points, and this difference increases to 13 IQ points for the old adolescents. > Beyond the observed small average sex difference in the general factor of intelligence (g), the boys' large advantage in mechanical reasoning (MR) must be strongly underscored. This sex difference is not explained by g, and therefore the probable contributions of what is measured by relevant subtests such as abstract reasoning (AR) or spatial relations (SR) can be excluded. The MR difference is still present with almost the same magnitude when the general factor of intelligence (g) is removed. It is also noteworthy that, for the old adolescents, more than half of the variance associated with numerical reasoning (NR) cannot be attributed to g. Thus, we suggest that mental processes captured by these psychological measures are behind the documented male advantage in STEM disciplines http://atavisionary.com/study-index/intelligence-psychometrics-psychology/sex-differences-on-g-and-non-g-intellectual-performance-reveal-potential-sources-of-stem-discrepancies/ http://atavisionary.com/study-index/intelligence-psychometri... An observed standard deviation of sex difference in measures of mechanical reasoning at the average of the distribution.