Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

70 Educability and Group Differences
neither contradicted nor discredited by evidence. . . . The preponderance
of the evidence is, in my opinion, less consistent with
a strictly environmental hypothesis than with a genetic hypothesis,
which, of course, does not exclude the influence of
environment or its interaction with genetic factors. (Jensen,
1969a, p. 82)
10. What Jencks means, of course, is ‘genetically superior in IQ*. It
is an interesting point that those who seem to oppose any hypothesis
of genetic differences also most frequently use the overly general
terms ‘inferior’ and ‘superior’ without the necessary qualification
of specifying the scale of the particular trait in question.
11. Most white-Negro mean differences reported in the literature probably
underestimate the true population difference because of a
statistical artifact that enters into any comparison between two
groups which are not sampled from the total range of scores in the
population, as when samples are drawn from schools or the armed
forces which may exclude IQs below some rather low selection cutoff.
If on some metrical trait x two normally distributed populations
differ by some amount d, and if samples are drawn only between
the values a and b (i.e., the sample is restricted to the range of
values a