1. Normal distribution
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  4. the bell curve.pdf(book)

The major purpose of Thp Bell Curve is to Curve, Herrnstein and Murray open this body of The bell curve: intelligence and class structure in American life. THE BELL CURVE Intelligence and Class Structure in American Life RICHARD J . HERRNSTEIN CHARLES MURRAY In our time, the ability to use and. The bell curve: intelligence and class structure in American life. / Richard J. Herrnstein, Charles Murray, p. cm. ISBN 1. Intellect. 1. Nature and.

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Bell Curve Pdf

š¯—£š¯——š¯—™ | Occasionally a book out of academia will break from scholarly Richard Herrnstein and Charles Murray's The Bell Curve: Intelligence. The Bell Curve: Intelligence and Class Structure in American Life is a book by psychologist Richard J. Herrnstein and political scientist Charles Murray. Bell-curve thinking, as a model of distribution of success and failure in standardized tests are revised until results conform to a bell curve; guidance coun-.

In probability theory , the normal or Gaussian or Gauss or Laplaceā€”Gauss distribution is a very common continuous probability distribution. Normal distributions are important in statistics and are often used in the natural and social sciences to represent real-valued random variables whose distributions are not known. The normal distribution is useful because of the central limit theorem. In its most general form, under some conditions which include finite variance , it states that averages of samples of observations of random variables independently drawn from independent distributions converge in distribution to the normal, that is, they become normally distributed when the number of observations is sufficiently large. Physical quantities that are expected to be the sum of many independent processes such as measurement errors often have distributions that are nearly normal. The normal distribution is sometimes informally called the bell curve. However, many other distributions are bell-shaped such as the Cauchy , Student's t - , and logistic distributions. The probability density of the normal distribution is. The simplest case of a normal distribution is known as the standard normal distribution. Authors may differ also on which normal distribution should be called the "standard" one. Every normal distribution is the exponential of a quadratic function:.

This leads directly to physical separation from the rest of society. Assertions are made, and conclusions reached, concerning the propensity of people involved in anti-social or otherwise undesirable behavior or situations to be below average when measured for cognitive ability. The conclusions reached are summarized as follows: Poverty - Low IQ is a strong precursor of poverty, even more so than the socioeconomic conditions in which people grow up. Schooling - Low IQ raises the likelihood of dropping out of school before completing high school, and decreases the likelihood of attaining a college degree.

Unemployment, Idleness and Injury - Low IQ is associated with persons who are unemployed, injured often, or idle removed themselves from the workforce. Family Matters - Low IQ correlates with high rates of divorce, lower rates of marriage, and higher rates of illegitimate births, Welfare Dependency - Low IQ increases the chances of chronic welfare dependency.

Parenting - Low IQ of mothers correlates with low birth weight babies, a child's poor motor skill and social development, and children's behavioral problems from age 4 and up.

Crime - Low IQ increases the risk of criminal behavior. Civility and Citizenship - Low IQ people vote least and care least about political issues. The controversy surrounding these topics, and the incredibly complex nature of the comparisons being made is acknowledged by the authors from the outset; the reader is cautioned to "read carefully".

The assertions and conclusions reached in this part of The Bell Curve include the following: Ethnic Differences in Cognitive Ability - East Asians typically earn higher IQ scores than white Americans, especially in the verbal intelligence areas. African-Americans typically earn IQ scores one full standard deviation below those of white Americans. Recent narrowing of the average IQ gap between black and white Americans about 3 IQ points is attributed to a lessening of low black scores and not an overall improvement in black scores on average.

The debate over genes versus environment influences on the race IQ gap is acknowledged. The Demography of Intelligence - Mounting evidence indicates that demographic trends are exerting downward pressure on the distribution of cognitive ability in the United States and that the pressures are strong enough to have social consequences.

Birth rates among highly educated women are falling faster than those of low IQ women. The IQ of the average immigrant of today is 95, lower than the national average, but more importantly the new immigrants are less brave, less hard working, less imaginative, and less self-starting than many of the immigrant groups of the past.

Social Behavior and the Prevalence of Low Cognitive Ability - For most of the worst social problems of our time, the people who have the problem are heavily concentrated in the lower portion of the cognitive ability spectrum. Solutions designed to solve or mitigate any of these problems must accommodate, even be focused towards, the low cognitive ability profile if they are to have any hope of succeeding.

All major domestic issues that we address must include a component that takes into account the predominant cognitive levels of the target population. For example, if we want to implement a training program for unemployed men, we should realize that fully half of the target group will have measured IQ below This should have a significant impact on the resulting social program or policy we establish.

Specifically, the discussions in this part of the book, the culmination of the author's efforts, include: Raising Cognitive Ability - If it were possible to significantly, consistently, and affordably raise intelligence, many of the negative consequences of societal low IQ could be mitigated or removed.

However, historical attempts to raise IQ using nutritional programs, additional formal schooling, and government preschool programs such as Head Start have proven to have little if any lasting impact on intelligence as measured by IQ tests. The one intervention that has consistently worked to raise intelligence is adoption form a bad family environment into a good one.

The authors recommend that children born to single mothers with low cognitive ability be voluntarily given up for adoption. The Leveling of American Education - The average American school child has not suffered from recent declines in overall school system measurements. Indeed, the focus of American public education has shifted more and more towards educating the average and below-average child to the exclusion of gifted children.

No more than one-tenth of one percent of federal education spending is targeted towards the gifted students. As American education has been "dumbed down" to accommodate the average and below average students, the gifted students have been allowed to slide by without developing their true potential.

The authors recommend that some federal education funds be shifted from disadvantaged programs to gifted programs, and that the federal government encourage parental choice in education through voucher programs, public school choice programs, or tax credits for education.

A final recommendation is for educators to once again view as one of the chief purposes of our educational system to educate the gifted because the future of society depends on them, an education that fosters wisdom and virtue through the ideal of the "educated man".

Affirmative Action in Higher Education - The edge given to minority applicants to college and graduate school is an extremely large advantage that puts them in a separate admissions process. Asians are a conspicuously unprotected minority due in large part to their above average intelligence scores. The cost of affirmative action in higher education includes the psychological consequences of students admitted under affirmative action programs, at lower cognitive ability levels, being seen as a low proportion of the overall student population, but a high proportion of the students doing poorly in school.

This can lead to increased racial animosity and the high black dropout rate on American campuses. The authors recommend a color-blind affirmative action, giving preference to members of disadvantaged groups when qualifications are similar.

Blacks have been overrepresented in white collar and professional occupations relative to the number of candidates in the IQ range from which these jobs are usually filled. The data suggest that aggressive affirmative action does produce large racial discrepancies in job performance in a given workplace. These trends are: 1 An increasingly isolated cognitive elite, 2 A merging of the cognitive elite with the affluent, and 3 A deteriorating quality of life for people at the bottom end of the cognitive ability distribution.

The authors see the continued polarization of society with the underclass anchored at the bottom, and the cognitive elite anchored at the top, restructuring the rules of society so that it becomes harder and harder for them to lose.

The author's denouement of their prognosis is the coming of the "custodial state - an expanded welfare state for the underclass that also keeps it out from underfoot". The custodial state will have the following consequences: 1 Childcare in the inner city will become primarily the responsibility of the state.

A Place for Everyone - In order to avoid the pessimistic custodial state conceptualized in the previous chapter, the authors propose a different scenario for American society in this chapter. The foundation to this alternative more positive scenario is the rethinking of equality and inequality. Herrnstein and Charles Murray, subtitled Intelligence and Class Structure in American Life, provides a superb and unusual opportunity to gain insight into the meaning of experiment as a method in science.

The primary desideratum in all experiments is reduction of confusing variables: we bring all the buzzing and blooming confusion of the external world into our laboratories and, holding all else constant in our artificial simplicity, try to vary just one potential factor at a time. But many subjects defy the use of such an experimental method particularly most social phenomena because importation into the laboratory destroys the subject of the investigation, and then we must yearn for simplifying guides in nature.

If the external world occasionally obliges by holding some crucial factors constant for us, we can only offer thanks for this natural boost to understanding. The first argument rehashes the tenets of social Darwinism as it was originally constituted. Social Darwinism has often been used as a general term for any evolutionary argument about the biological basis of human differences, but the initial nineteenth century meaning referred to a specific theory of class stratification within industrial societies, and particularly to the idea that there was a permanently poor underclass consisting of genetically inferior people who had precipitated down into their inevitable fate.

The theory arose from a paradox of egalitarianism: as long as people remain on top of the social heap by accident of a noble name or parental wealth, and as long as members of despised castes cannot rise no matter what their talents, social stratification will not reflect intellectual merit, and brilliance will be distributed across all classes; but when true equality of opportunity is attained, smart people rise and the lower classes become rigid, retaining only the intellectually incompetent.

This argument has attracted a variety of twentieth-century champions, including the Stanford psychologist Lewis M. Terman, who imported Alfred Binet's original test from France, developed the Stanford-Binet IQ test, and gave a hereditarian interpretation to the results one that Binet had vigorously rejected in developing this style of test ; Prime Minister Lee Kuan Yevv of Singapore, who tried to institute a eugenics program of rewarding well-educated women for higher birth rates; and Richard Herrnstein, a co-author of The Bell Curve and also the author of a Atlantic Monthly article that presented the same argument without the documentation.

The general claim is neither uninteresting nor illogical, but it does require the validity of four shaky premises, all asserted but hardly discussed or defended by Herrnstein and Murray. Intelligence, in their formulation, must be depictable as a single number, capable of ranking people in linear order, genetically based, and effectively immutable.

If any of these premises are false, their entire argument collapses.

For example, if all are true except immutability, then programs for early intervention in education might work to boost IQ permanently, just as a pair of eyeglasses may correct a genetic defect in vision. The central argument of The Bell Curve fails because most of the premises are false. This argument is as old as the study of race, and is almost surely fallacious.

The last generation's discussion centered on Arthur Jensen's book Bias in Mental Testing far more elaborate and varied than anything presented in The Bell Curve, and therefore still a better source for grasping the argument and its problems , and on the cranky advocacy of William Shockley, a Nobel Prize-winning physicist.

The central fallacy in using the substantial heritability of within-group IQ among whites, for example as an explanation of average differences between groups whites versus blacks, for example is now well known and acknowledged by all, including Herrnstein and Murray, but deserves a restatement by example.

Take a trait that is far more heritable than anyone has ever claimed IQ to be but is politically uncontroversial body height. Suppose that I measure the heights of adult males in a poor Indian village beset with nutritional deprivation, and suppose the average height of adult males is five feet six inches.

Heritability within the village is high, which is to say that tall fathers they may average five feet eight inches tend to have tall sons, while short fathers five feet four inches on average tend to have short sons. But this high heritability within the village does not mean that better nutrition might not raise average height to five feet ten inches in a few generations.

Normal distribution

Similarly, the well-documented fifteen-point average difference in IQ between blacks and whites in America, with substantial heritability of IQ in family lines within each group, permits no automatic conclusion that truly equal opportunity might not raise the black average enough to equal or surpass the white mean. The authors omit facts, misuse statistical methods, and seem unwilling to admit the consequences of their own words.

Murray and Herrnstein simply declare that the issue has been decided, as in this passage from their Republic article: "Among the experts, it is by now beyond much technical dispute that there is such a thing as a general factor of cognitive ability on which human beings differ and that this general factor is measured reasonably well by a variety of standardized tests, best of all by IQ tests designed for that purpose.

The fact that Herrnstein and Murray barely mention the factor-analytic argument forms a central indictment of The Bell Curve and is an illustration of its vacuousness. How can the authors base an page book on a claim for the reality of IQ as measuring a genuine, and largely genetic, general cognitive ability and then hardly discuss, either pro or con, the theoretical basis for their certainty?

And here, for once, I agree entirely. As a card carrying First Amendment near absolutist, I applaud the publication of unpopular views that some people consider dangerous.

I am delighted that The Bell Curve was written so that its errors could be exposed, for Herrnstein and Murray are right to point out the difference between public and private agendas on race, and we must struggle to make an impact on the private agendas as well.

But The Bell Curve is scarcely an academic treatise in social theory and population genetics. It is a manifesto of conservative ideology; the book's inadequate and biased treatment of data displays its primary purpose advocacy. The text evokes the dreary and scary drumbeat of claims associated with conservative think tanks: reduction or elimination of welfare, ending or sharply curtailing affirmative action in schools and workplaces, cutting back Head Start and other forms of preschool education, trimming programs for the slowest learners and applying those funds to the gifted.

I would love to see more attention paid to talented students, but not at this cruel price. We must fight the doctrine of The Bell Curve both because it is wrong and because it will, if activated, cut off all possibility of proper nurturance for everyone's intelligence. Of course, we cannot all be rocket scientists or brain surgeons, but those who can't might be rock musicians or professional athletes and gain far more social prestige and salary thereby , while others will indeed serve by standing and waiting.

And if no real entity answering to the name could be found, men did not for that reason suppose that none existed, but imagined that it was something particularly abstruse and mysterious.

E pluribus unum. Some of the analysis and a good deal of the tone are reasonable. Yet the science in the book was questionable when it was proposed a century ago, and it has now been completely supplanted by the development of the cognitive sciences and neurosciences.

The policy recommendations of the book are also exotic, neither following from the analyses nor justified on their own. I became increasingly disturbed as I read and reread this page work. I gradually realized I was encountering a style of thought previously unknown to me: scholarly brinkmanship. Whether concerning an issue of science, policy, or rhetoric, the authors come dangerously close to embracing the most extreme positions, yet in the end shy away from doing so.

Normal distribution - Wikipedia

Discussing scientific work on intelligence, they never quite say that intelligence is all important and tied to one's genes; yet they signal that this is their belief and that readers ought to embrace the same conclusions.

Discussing policy, they never quite say that affirmative action should be totally abandoned or that childbearing or immigration by those with low IQs should be curbed; yet they signal their sympathy for these options and intimate that readers ought to consider these possibilities. The Bell Curve is not as controversial as its reputation would lead one to believe and most of the book is not about race at all. The statement was written by psychologist Linda Gottfredson and published in The Wall Street Journal in and subsequently reprinted in Intelligence , an academic journal.

Of the who were invited by mail to sign the document, responded, with 52 agreeing to sign and 48 declining. Eleven of the 48 who declined to sign claimed that the statement or some part thereof did not represent the mainstream view of intelligence.

They agreed that: Intelligence test scores have a correlation of 0. The Flynn effect shows that environmental factors can produce differences of at least this magnitude, but that effect is mysterious in its own right. There is even less empirical support for a genetic interpretation. In short, no adequate explanation of the differential between the IQ means of Blacks and Whites is presently available. The APA journal that published the statement, American Psychologist , subsequently published eleven critical responses in January Many criticisms were collected in the book The Bell Curve Debate.

Criticism of alleged assumptions[ edit ] Criticism by Stephen Jay Gould[ edit ] Stephen Jay Gould wrote that the "entire argument" of the authors of The Bell Curve rests on four unsupported, and mostly false, assumptions about intelligence: [9] [20] Intelligence must be reducible to a single number.

Intelligence must be capable of rank ordering people in a linear order. Intelligence must be primarily genetically based. Intelligence must be essentially immutable. But in an interview with Frank Miele, co-author Charles Murray denied making any of these assumptions. Interviewer: Let me go back to Gould's four points.

Is there any one of those that you think is not a fair and accurate statement of what you said? Murray: All four of them. Murray: No. In The Bell Curve, we say of the I. That has been a failure.

On the other hand, there have been a variety of ways in which there are distinctions among different types of intelligence that are useful, such as the distinction between verbal, visual and spacial intelligence.

And we talk about the different ways these different skills lead to success in occupations. And we talk, somewhat sympathetically, about the notion that there are, in Howard Gardner's words, multiple intelligences. We are a little dubious about applying the word "intelligence" to them, but we are very sympathetic that there are large domains of human talent that are not encompassed in the word "intelligence. Interviewer: You are not a determinist.

You are not saying everything is in the genes. You think free will is a meaningful concept. Murray: Yes, and so did Dick Herrnstein Heckman's reanalysis of the evidence used in The Bell Curve found contradictions: The factors that explain wages receive different weights than the factors that explain test scores.

More than g is required to explain either. Other factors besides g contribute to social performance, and they can be manipulated. Lucas, Ann Swidler , and Kim Voss in the book Inequality by Design recalculated the effect of socioeconomic status, using the same variables as The Bell Curve, but weighting them differently. They found that if IQ scores are adjusted, as Herrnstein and Murray did, to eliminate the effect of education , the ability of IQ to predict poverty can become dramatically larger, by as much as 61 percent for whites and 74 percent for blacks.

According to the authors, Herrnstein and Murray's finding that IQ predicts poverty much better than socioeconomic status is substantially a result of the way they handled the statistics.

Korenman and Winship concluded: " In addition, Herrnstein and Murray's measure of parental socioeconomic status SES fails to capture the effects of important elements of family background such as single-parent family structure at age As a result, their analysis gives an exaggerated impression of the importance of IQ relative to parents' SES, and relative to family background more generally.

Estimates based on a variety of methods, including analyses of siblings, suggest that parental family background is at least as important, and may be more important than IQ in determining socioeconomic success in adulthood. This work argues that much of the public response was polemic, and failed to analyze the details of the science and validity of the statistical arguments underlying the book's conclusions.

Matthews writes that part of The Bell Curve's analysis is based on the AFQT "which is not an IQ test but designed to predict performance of certain criterion variables".

The Bell Curve

He continues: Ironically, the authors delete from their composite AFQT score a timed test of numerical operations because it is not highly correlated with the other tests. Yet it is well known that in the data they use, this subtest is the single best predictor of earnings of all the AFQT test components.

The fact that many of the subtests are only weakly correlated with each other, and that the best predictor of earnings is only weakly correlated with their "g-loaded" score, only heightens doubts that a single-ability model is a satisfactory description of human intelligence. It also drives home the point that the "g-loading" so strongly emphasized by Murray and Herrnstein measures only agreement among testsā€”not predictive power for socioeconomic outcomes.

By the same token, one could also argue that the authors have biased their empirical analysis against the conclusions they obtain by disregarding the test with the greatest predictive power. Using the same data, we demonstrate their finding is very fragile.

the bell curve.pdf(book)

Tittle and Thomas Rotolo found that the more the written, IQ-like, examinations are used as screening devices for occupational access, the stronger the relationship between IQ and income. Thus, rather than higher IQ leading to status attainment because it indicates skills needed in a modern society, IQ may reflect the same test-taking abilities used in artificial screening devices by which status groups protect their domains. Hauser write that Herrnstein and Murray provide scant evidence of growth in cognitive sorting.

Using data from the General Social Survey, they tested each of these hypotheses using a short verbal ability test which was administered to about 12, American adults between and ; the results provided no support for any of the trend hypotheses advanced by Herrnstein and Murray. One chart in The Bell Curve purports to show that people with IQs above have become "rapidly more concentrated" in high-IQ occupations since But Robert Hauser and his colleague Min-Hsiung Huang retested the data and came up with estimates that fell "well below those of Herrnstein and Murray.

Chomsky criticized the assumptions that people only seek occupations based on material gain. He argued that Herrnstein would not want to become a baker or lumberjack even if he could earn more money that way.

He also criticized the assumption that such a society would be fair with pay based on value of contributions. He argued that because there are already unjust great inequalities, people will often be paid, not for valuable contributions to society, but to preserve such inequalities. He gives the example of women wearing earrings : To borrow an example from Ned Block, "some years ago when only women wore earrings, the heritability of having an earring was high because differences in whether a person had an earring was due to a chromosomal difference, XX vs.

Race and intelligence[ edit ] See also: History of the race and intelligence controversy One part of the controversy concerned the parts of the book which dealt with racial group differences on IQ and the consequences of this.

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