How misinformed are people about psychometrics?

Data from here:

No one informed about this subject can give this book more than 2, and it really should only get 1’s for this pathetic performance, even if well-written.

However, the rating stats show that:

rating frequency % #
36% 974
39% 1048
19% 509
3% 100
1% 29

Pathetic. Jensen was right when he wrote:

I had begun by trying, for the sake of scholarly thoroughness, merely to write
a short chapter for my book on the ‘culturally disadvantaged’ that I expected
would succinctly review the so-called nature-nurture issue only to easily dismiss
it as being of little or no importance for the subsequent study of the causes of
scholastic failure and success. I delved into practically all the available literature
on the genetics of intelligence, beginning with the works of the most prominent
investigator in this field, Sir Cyril Burt, whom I had previously heard give a
brilliant lecture entitled The Inheritance of Mental Ability’ at University
College, London in 1957. The more I read in this field, the less convinced I
became of the prevailing belief in the all-importance of environment and learning
as the mechanisms of individual and group differences in general ability and
scholastic aptitude. I felt even somewhat resentful of my prior education, that I
could have gone as far as I had—already a fairly well-recognized professor of
educational psychology—and yet could have remained so unaware of the crucial
importance of genetic factors for the study of individual differences. It was little
consolation that I had been ‘in good company’ in my ignorance of genetics; in
fact, that aspect of the situation seemed even more alarming to me. I was
overwhelmed by the realization of the almost Herculean job that would be
needed to get the majority of psychologists and educators fully to recognize the
importance of genetics for the understanding of variation in psychological traits.
Hence, rather than attempting at first to add small increments of original
empirical research to the body of knowledge on the genetics of human abilities, I
thought my most useful role at that point was a primarily didactic one. Most of
my thirty-five articles and four books dealing with genetics are of that nature. But
in the course of marshaling the scattered existing research evidence, and trying to
make the most sense of it, I noted certain methodological problems and
formulations that called for criticism and reformulation. One was Karl
Holzinger’s conceptually muddled index of heritability based on monozygotic
(MZ) and dizygotic (DZ) twins, for which I substituted a more defensible
formula that comes closer to the theoretical definition of heritability and also
takes account of assortative mating in estimating the heritability of a trait (Jensen,
1967). Another was the estimation of the limits of genotype×environment
covariance in IQ, based on data from MZ and DZ twins (Jensen, 1976b). A
theoretical paper on the possible explanation of race differences and a race×sex
interaction in spatial ability in terms of sex-linkage of a hypothesized recessive
gene that enhances spatial visualization ability (Jensen, 1975a), although an
interesting and plausible theory, has been undercut in recent years by the failure
to find consistent evidence for any sex-linkage in the genetic conditioning of
spatial ability. My empirical findings in behavior genetics have concerned the
heritability of memory span (Jensen and Marisi, 1979) and the effects of
inbreeding depression on general ability (Agrawal, Sinha and Jensen, 1984;
Jensen, 1983b). The study of inbreeding depression seems to me especially
important in the study of human abilities, because inbreeding depression indicates
genetic dominance, and the presence and degree of dominance are related to
natural selection for the trait in the course of its biological evolution. It was of
great interest to me to discover, for example, that of the several ability factors
that can be extracted from the various subtests of the Wechsler Intelligence Scale
for Children, the one that shows the greatest susceptibility to inbreeding
depression is the g factor (Jensen, 1983b). This finding indicates that one of our
most widely used standard psychometric tests of intelligence yields scores that
reflect some part of the variance in the biological intelligence that has developed
in the course of human evolution.

From: Modgil, Sohan, and Celia Modgil, eds. Arthur Jensen: Consensus and Controversy. Vol. 4. Routledge, 1987.

Last chapter (Jensen’s).