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

Race Differences in Intelligence 167
or measured any set of environmental conditions on which the
Negro and white populations differ, on the average, by even half
as much as 3 sigmas.8 A multiple point-biserial correlation (R)
between a host of environmental measures and the Negro-white
dichotomy (treated as a quantized variable) would have to be
«— I.O c r— ►
XN= 85 Xw=100
Phenotypes cr = 15 IQ points
Total Environmental Effects a = 4 .7 4 IQ points
3etw een- Families Environmental Effects a =3.35 IQ points
Figure 7.2 The top curves represent two IQ distributions each
with a = 15 IQ points and the means differing by 15 points or lcr.
The middle set of curves shows the effect of removing all genetic
variance, leaving only the total environmental variance; the means
then differ by 3-2cr of total environmental effects. The lower curves
show the effect of removing both the genetic and the withinfamilies
environmental variance, leaving only between-families
environmental variance; the means then differ by 4-5(7 of betweenfamilies
environmental effects. The area under all curves is the same.