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

250 Educability and Group Differences
the Mexican homes Spanish or another foreign language is spoken
exclusively, as compared with 1-1 percent for whites and 0-5
percent for Negroes. Many of the parents of the Mexican children
grew up in Mexico where they had little or no education. Most of
them came to the central valley of California (in which the present
study was conducted) as agricultural workers living in overcrowded,
unsanitary migratory camps that follow the fruit and vegetable
crops. Because of the nomadic life of the parents, many of these
Grade
Figure 12.1 Mean T scores (£ = 50, SD = 10) on Raven’s
Progressive Matrices.
children have poor records of school attendance. The adjusted
achievement means (the last two columns of Table 12.1) refer to
the achievement test means after they have been adjusted by
analysis of covariance using intelligence and SES as the control
variables. In effect, these two columns represent the sigma units by
which the minority groups fall below the white in achievement when
all groups are statistically equated for intelligence and SES. The
achievement differences that remain are practically negligible and can
be even further reduced by including additional control variables,
such as motivational and personality tests, in the covariance analysis.
On Raven’s Progressive Matrices, a non-verbal, culture-fair test