送交者: xj 于 2006-4-14, 12:45:30:
回答: 不用逻辑也可以说事儿：两个分布的偏差远大于两个分布的平均差时， 由 mirror 于 2006-4-14, 07:00:39:
even the two distributions have largely overlap, and each standard deviation is larger than the difference of means, for example, the STD for IQ is 10, while the difference of two IQ means is 5.
However, when doing comparison, the difference of means should use the standard deviation of the difference of means. So the small difference of IQ means can be significant.
Yes, the large overlap between two distributions suggests that the difference between them may have no practical meanings, because a large percent of people in the "lower" group may in fact be better than average of the other group.
The point is, that there is a slight detectable difference in IQ means between blacks and whites, and the difference can be due to genetics or environmental factors, or more likely, both.