Vince Lepore
01-07-2005, 02:33 PM
From:
http://www.geocities.com/rnseitz/Definition_of_IQ.html
IQ
It's a matter of everyday experience that some people are smarter than others. But how do we measure "smartness"?
In 1905, a French psychologist by the name of Alfred Binet, working with a physician-associate, Theodore Simon, developed the Binet Simon Test designed to measure the intelligence of retarded children, based upon their observations that.
(1) Just as children grow taller as they grow older, they grow more mentally capable as they grow older; and
(2) Some children can perform at age and equivalent-grade levels above their chronological ages, while other children perform at age and equivalent-grade levels below their chronological ages. For example, a few 6-year-olds could perform as well on the Binet Simon mental tests as the average 8-year-old, while a few 6-year-olds could only perform as well as the average 4-year-old.
In 1911, the concept of "mental age" (as distinguished from "chronological age")was introduced. The 6-year-old who performed as well as the average 8-year-old was assigned a mental age of 8, while the 6-year-old who performed only as well as a 4-year-old was assigned a mental age of 4.
What Is "IQ"?
It was also observed that the gaps between children's mental ages and their chronological ages widened as the children got older. The 6-year-old with the mental age of 8 had a mental age of 12 by the time he was 9 and a mental age of 16 by the time he was12. Similarly, the 6-year-old with a mental age of 4 had a mental age of 6 when he was 9 and a mental age of 8 when he was 12. In 1912, the German psychologist, William Stern, noticed that even though the gap between mental age and chronological age widens as a child matures, the ratio of mental age to chronological age remains constant (and, as we will see, remains essentially constant throughout life). This constant ratio of mental age divided by chronological age was given the name "Intelligence Quotient". Actually, the intelligence quotient is defined as 100 times the Mental Age (MA) divided by the Chronological Age (CA).
IQ = 100 MA/CA.
Mental Age for Adults
At approximately. the age of 16, mental age, like height, stops increasing. Until 1960, it was customary to use 16 as the divisor for mental age among adults. Actually, certain mental functions increase slowly and slightly after the age of 16, peaking in the 20's, with others remaining stable or even rising slightly up to the age of 60 or so. With some individuals, vocabulary may increase over time.
The Practical Significance of IQ
The average IQ of the population as a whole is, by definition, 100. IQs range from 0 to above 200, and among children, to above 250. However, about 50% of the population have IQs between 89 and 111, and about 80% of the population have IQs ranging between 80 and 120, with 10% lying below 80, and 10% falling above 120.
For IQs below 120, IQ is the best predictor of socioeconomic status of any psychometric measurement. In more complex jobs, IQ is better than even education or experience at predicting job performance. In her article "The General Intelligence Factor", Scientific American Presents "Exploring Intelligence", pg. 24, 1999, Linda Gottfredson states,
"Adults in the bottom 5% of the IQ distribution (below 75) are very difficult to train and are not competitive for any occupation on the basis of ability. Serious problems in training low-IQ military recruits during World War II led Congress to ban enlistment from the lowest 10% (below 80) of the population, and no civilian occupation in modern economies routinely recruits its workers from that below-80 range. Current military enlistment standards exclude any individual whose IQ is below about 85."
"Persons of average IQ (between 90 and 100) are not competitive for most professional and executive-level work but are easily trained for the bulk of jobs in the American economy. By contrast, individuals in the top 5 percent of the adult population can essentially train themselves, and few occupations are beyond their reach mentally."
"People with IQs between 75 and 90 are 88 times more likely to drop out of high school, seven times more likely to be jailed, and five times more likely as adults to live in poverty than people with IQs between 110 and 125. The 75-to-90 IQ woman is eight times more likely to become a chronic welfare recipient, and four times as likely to bear an illegitimate child than the 110-to-125-IQ woman."
In his book, "Straight Talk About Mental Tests", The Free Press, A Division of the Macmillan Publishing Co., Inc., New York, 1981, pg. 12, Dr. Arthur Jensen cites the following four IQ thresholds:
(1) An IQ of 50 or below. This is the threshold below which most adults cannot cope outside of an institution. They can typically be taught to read at a 3rd or 4th grade level. However, they cannot normally function in the customary classroom setting, and they require special training programs.
(2) An IQ between 50 and 75. At this level of intelligence, they generally cannot complete elementary school. Most adults will need smarter help in coping with the world.
(3) An IQ between 75 and 105. Children in this IQ range are not generally able to complete a college prep course in high school.
(4) An IQ between 105 and 115. May graduate from college but generally, not with grades that would qualify them for graduate school.
(5) An IQ above 115. No restrictions.
For IQs in these ranges, the influence of IQ upon socioeconomic sttus is dramatic. 31% of those with IQs below 75 were on welfare, compared with 8% of those in the 90 to 110 IQ interval, and 0% in those with IQs above 125. 55% of mothers with IQs below 75 went on welfare after the birth of the first child, compared with 12% of those with IQs between 90 and 110, and 1% of those with IQs above 125. Income is highly dependent upon IQ up to an IQ-level of about 125.
120 to 125 Ph. D.'s. Manager, professor, accountant
125 to 132 Any Ph. D. at 3rd-Tier Schools Attorney, editor, executive
132 to 137 No limitations. Eminent professor, editor
137 to 150 No limitations. Leading math, physics professor
150 to 160 No limitations Lincoln, Copernicus, Jefferson
160 to 174 No limitations Descartes, Einstein, Spinoza
174 to 200 No limitations Shakespeare, Goethe, Newton
To gain a clearer perspective regarding what this means in terms of our daily contacts with people, let's take a trip down to a local Walmart. Let's suppose we're visiting the only Walmart in a small, rural town, so that neighborhood inhomogeneities don't affect the cohort of shoppers we'll find at the store. That way, we'll be seeing a nearly random cross-section of the public on our trip.
OK. Here we are at Walmart. I can already see quite a few people out here in the parking lot.
Let's suppose that we're going to see 100 other customers while we're here shopping, and then consider their breakdown by IQ. On the basis of the law of averages, we'd expect to see one person here with an IQ below 64! There'd be someone else with an IQ between 64 and 68. There should be 3 more with IQs between 69 and 75. In other words, if this is a random crowd, 1 out of 20 people we're going to meet will have IQs below 75, and will be seriously retarded! (I guess we're lucky the world works as well as it does.) Keep your eyes peeled. See if you can spot 'em. About 1 out of 10 people we'll walk past here at Walmart has an IQ below 80, or about 10 of the 100 people who cross our paths here in the store! Hey, look! Does she look kind of sagaciously-challenged to you? One out of 5, or 20 of the 100 people we're seeing have IQs below 87, with about 1 in 10 in the 80 to 87 IQ range. Half the crowd, or 50 out of the 100, has below-average intelligence! And of course, the other half has above-average intelligence. Twenty of them (1 out of 5) have IQs above 113. Ten of them, or 1 in 10, have IQs above 120. Five of them have IQs above 125, and have the potential to become university professors with Ph. D's. Two of them have IQs of 132 or above, and are potential members of Mensa. One of them has an IQ above 136.
Did you spot them? I saw one or two possible candidates, but I suppose we'd better not walk up and say,
"Pardon me, ma'am. You look mentally challenged. Are you?"
She might hit us with her purse.
If we spent time at a large urban mall, we might rub elbows with 1,000 shoppers. In an average, unenriched setting, where we saw 1,000 other shoppers at Christmas-time, IQs might typically be expected to range between 50 and 150. In a blue-stocking suburb like Norcross or Corte Madera, we might expect to find one or more folk with IQs above 150, and perhaps, an individual or two with an IQ above 160. This is a huge range of IQs.
I think that the range of intellects that we walk past in the world is awesome. The span between top and bottom among 100 people chosen at random would be about 75 points of deviation IQ, or more than 80 points of ratio IQ. And we've been walking past them every day.
This isn't the whole story. It's mentioned below that even on culture-fair tests, the average IQ of our African-American population falls about one standard deviation below those of the other components of our population. This means that 1 out of 10 African-Americans has an IQ below 59, and only about 2 Africans in 1,000 can qualify for Mensa. So most probably, on our trip to Walmart, we're going see an African-American with an IQ of 60 or below (mental age of 10).
Until I wrote this up this afternoon, I had never stopped to think just what intellectual diversity awaits us at our local shopping centers. Half the people we meet in cars on the road have below-average intelligence, and 1 in 20 must be seriously retarded, with a mental age of 12 or below. Ouch! I think I'll ride my bike on back streets to the store.
Can Intelligence Be Measured With a Single Number?
Yes and no. One of the most serious criticisms of using a single number to assess intelligence is that people may be stronger in certain areas such as verbal skills, logical aptitude or spatial visualization than in others. Drs. Richard Feynmann and Albert Einstein would be examples of geniuses who were extremely strong mathematically while being relatively weak verbally. More commonly, though, purely intellectual abilities tend to be uniformly high or uniformly low in a given individual, leading to the concept of an underlying "g" or "general intelligence" that powers all the specialized intellectual aptitudes. Still, this doesn't happen with everyone, and the exceptions, like Richard Feynmann and Albert Einstein, are very important. Tests like the Wechsler Adult Intelligence Scale (WAIS) consist of a number of subtests that are scored separately and can measure the profile for an individual. (Dr. Howard Gardner has defined seven types of intelligence, while Dr. Robert Sternberg has identified three.)
It's also easier to make an IQ score that's lower than your true IQ than it is to make a score that's higher. Taking a test on a bad day, or spending too much time on a few difficult items could artificially lower one's score. The best results are obtained when more than one test is administered.
What Does Adult IQ Mean?
Generally, one's mental age stops rising rapidly when one reaches the latter teens--e. g., 16. Consequently, on some IQ tests, "16" was taken as the chronological-age divisor in an IQ calculation for adults. The Wechsler Adult Intelligence Scale is calibrated for all ages up to 70, with chronological-age divisors appropriate to every age 70 or below.
The average IQ is, by definition, 100. To get an idea what this means, someone with an IQ of 80 or below is considered to be marginally able to cope with the adult world. People with IQ's of 80 or below typically work as unskilled laborers such as lawn maintenance and trash pickup. They generally need help from friends or family to manage life's complications. About 10% of the population has an IQ of 80 or below.
People with IQ's of 80-90 are a little on the slow side but may be found in fast-food restaurants, day-care centers, etc. They may also be found in unskilled jobs. About 16% of the population has IQ's in this range.
People with IQ's of 90-110 generally occupy semi-skilled positions, including typists, receptionists, assembly line workers, and checkout clerks. They are able to keep up with the world, and comprise about 46% of the public.
People with IQ's in the 110 to 120 range fill the skilled trades and include some tool and die makers, teachers, and Ph. D.'s among their ranks. They also make up 16% of the population.
People with IQ's of 120 and above tend to staff the professions as doctors, dentists, lawyers, teachers, and college professors. They fall in the upper 10% of the population.
The average IQ of all college professors is 130, which lies within the upper 3% of the general public.
http://www.geocities.com/rnseitz/Definition_of_IQ.html
IQ
It's a matter of everyday experience that some people are smarter than others. But how do we measure "smartness"?
In 1905, a French psychologist by the name of Alfred Binet, working with a physician-associate, Theodore Simon, developed the Binet Simon Test designed to measure the intelligence of retarded children, based upon their observations that.
(1) Just as children grow taller as they grow older, they grow more mentally capable as they grow older; and
(2) Some children can perform at age and equivalent-grade levels above their chronological ages, while other children perform at age and equivalent-grade levels below their chronological ages. For example, a few 6-year-olds could perform as well on the Binet Simon mental tests as the average 8-year-old, while a few 6-year-olds could only perform as well as the average 4-year-old.
In 1911, the concept of "mental age" (as distinguished from "chronological age")was introduced. The 6-year-old who performed as well as the average 8-year-old was assigned a mental age of 8, while the 6-year-old who performed only as well as a 4-year-old was assigned a mental age of 4.
What Is "IQ"?
It was also observed that the gaps between children's mental ages and their chronological ages widened as the children got older. The 6-year-old with the mental age of 8 had a mental age of 12 by the time he was 9 and a mental age of 16 by the time he was12. Similarly, the 6-year-old with a mental age of 4 had a mental age of 6 when he was 9 and a mental age of 8 when he was 12. In 1912, the German psychologist, William Stern, noticed that even though the gap between mental age and chronological age widens as a child matures, the ratio of mental age to chronological age remains constant (and, as we will see, remains essentially constant throughout life). This constant ratio of mental age divided by chronological age was given the name "Intelligence Quotient". Actually, the intelligence quotient is defined as 100 times the Mental Age (MA) divided by the Chronological Age (CA).
IQ = 100 MA/CA.
Mental Age for Adults
At approximately. the age of 16, mental age, like height, stops increasing. Until 1960, it was customary to use 16 as the divisor for mental age among adults. Actually, certain mental functions increase slowly and slightly after the age of 16, peaking in the 20's, with others remaining stable or even rising slightly up to the age of 60 or so. With some individuals, vocabulary may increase over time.
The Practical Significance of IQ
The average IQ of the population as a whole is, by definition, 100. IQs range from 0 to above 200, and among children, to above 250. However, about 50% of the population have IQs between 89 and 111, and about 80% of the population have IQs ranging between 80 and 120, with 10% lying below 80, and 10% falling above 120.
For IQs below 120, IQ is the best predictor of socioeconomic status of any psychometric measurement. In more complex jobs, IQ is better than even education or experience at predicting job performance. In her article "The General Intelligence Factor", Scientific American Presents "Exploring Intelligence", pg. 24, 1999, Linda Gottfredson states,
"Adults in the bottom 5% of the IQ distribution (below 75) are very difficult to train and are not competitive for any occupation on the basis of ability. Serious problems in training low-IQ military recruits during World War II led Congress to ban enlistment from the lowest 10% (below 80) of the population, and no civilian occupation in modern economies routinely recruits its workers from that below-80 range. Current military enlistment standards exclude any individual whose IQ is below about 85."
"Persons of average IQ (between 90 and 100) are not competitive for most professional and executive-level work but are easily trained for the bulk of jobs in the American economy. By contrast, individuals in the top 5 percent of the adult population can essentially train themselves, and few occupations are beyond their reach mentally."
"People with IQs between 75 and 90 are 88 times more likely to drop out of high school, seven times more likely to be jailed, and five times more likely as adults to live in poverty than people with IQs between 110 and 125. The 75-to-90 IQ woman is eight times more likely to become a chronic welfare recipient, and four times as likely to bear an illegitimate child than the 110-to-125-IQ woman."
In his book, "Straight Talk About Mental Tests", The Free Press, A Division of the Macmillan Publishing Co., Inc., New York, 1981, pg. 12, Dr. Arthur Jensen cites the following four IQ thresholds:
(1) An IQ of 50 or below. This is the threshold below which most adults cannot cope outside of an institution. They can typically be taught to read at a 3rd or 4th grade level. However, they cannot normally function in the customary classroom setting, and they require special training programs.
(2) An IQ between 50 and 75. At this level of intelligence, they generally cannot complete elementary school. Most adults will need smarter help in coping with the world.
(3) An IQ between 75 and 105. Children in this IQ range are not generally able to complete a college prep course in high school.
(4) An IQ between 105 and 115. May graduate from college but generally, not with grades that would qualify them for graduate school.
(5) An IQ above 115. No restrictions.
For IQs in these ranges, the influence of IQ upon socioeconomic sttus is dramatic. 31% of those with IQs below 75 were on welfare, compared with 8% of those in the 90 to 110 IQ interval, and 0% in those with IQs above 125. 55% of mothers with IQs below 75 went on welfare after the birth of the first child, compared with 12% of those with IQs between 90 and 110, and 1% of those with IQs above 125. Income is highly dependent upon IQ up to an IQ-level of about 125.
120 to 125 Ph. D.'s. Manager, professor, accountant
125 to 132 Any Ph. D. at 3rd-Tier Schools Attorney, editor, executive
132 to 137 No limitations. Eminent professor, editor
137 to 150 No limitations. Leading math, physics professor
150 to 160 No limitations Lincoln, Copernicus, Jefferson
160 to 174 No limitations Descartes, Einstein, Spinoza
174 to 200 No limitations Shakespeare, Goethe, Newton
To gain a clearer perspective regarding what this means in terms of our daily contacts with people, let's take a trip down to a local Walmart. Let's suppose we're visiting the only Walmart in a small, rural town, so that neighborhood inhomogeneities don't affect the cohort of shoppers we'll find at the store. That way, we'll be seeing a nearly random cross-section of the public on our trip.
OK. Here we are at Walmart. I can already see quite a few people out here in the parking lot.
Let's suppose that we're going to see 100 other customers while we're here shopping, and then consider their breakdown by IQ. On the basis of the law of averages, we'd expect to see one person here with an IQ below 64! There'd be someone else with an IQ between 64 and 68. There should be 3 more with IQs between 69 and 75. In other words, if this is a random crowd, 1 out of 20 people we're going to meet will have IQs below 75, and will be seriously retarded! (I guess we're lucky the world works as well as it does.) Keep your eyes peeled. See if you can spot 'em. About 1 out of 10 people we'll walk past here at Walmart has an IQ below 80, or about 10 of the 100 people who cross our paths here in the store! Hey, look! Does she look kind of sagaciously-challenged to you? One out of 5, or 20 of the 100 people we're seeing have IQs below 87, with about 1 in 10 in the 80 to 87 IQ range. Half the crowd, or 50 out of the 100, has below-average intelligence! And of course, the other half has above-average intelligence. Twenty of them (1 out of 5) have IQs above 113. Ten of them, or 1 in 10, have IQs above 120. Five of them have IQs above 125, and have the potential to become university professors with Ph. D's. Two of them have IQs of 132 or above, and are potential members of Mensa. One of them has an IQ above 136.
Did you spot them? I saw one or two possible candidates, but I suppose we'd better not walk up and say,
"Pardon me, ma'am. You look mentally challenged. Are you?"
She might hit us with her purse.
If we spent time at a large urban mall, we might rub elbows with 1,000 shoppers. In an average, unenriched setting, where we saw 1,000 other shoppers at Christmas-time, IQs might typically be expected to range between 50 and 150. In a blue-stocking suburb like Norcross or Corte Madera, we might expect to find one or more folk with IQs above 150, and perhaps, an individual or two with an IQ above 160. This is a huge range of IQs.
I think that the range of intellects that we walk past in the world is awesome. The span between top and bottom among 100 people chosen at random would be about 75 points of deviation IQ, or more than 80 points of ratio IQ. And we've been walking past them every day.
This isn't the whole story. It's mentioned below that even on culture-fair tests, the average IQ of our African-American population falls about one standard deviation below those of the other components of our population. This means that 1 out of 10 African-Americans has an IQ below 59, and only about 2 Africans in 1,000 can qualify for Mensa. So most probably, on our trip to Walmart, we're going see an African-American with an IQ of 60 or below (mental age of 10).
Until I wrote this up this afternoon, I had never stopped to think just what intellectual diversity awaits us at our local shopping centers. Half the people we meet in cars on the road have below-average intelligence, and 1 in 20 must be seriously retarded, with a mental age of 12 or below. Ouch! I think I'll ride my bike on back streets to the store.
Can Intelligence Be Measured With a Single Number?
Yes and no. One of the most serious criticisms of using a single number to assess intelligence is that people may be stronger in certain areas such as verbal skills, logical aptitude or spatial visualization than in others. Drs. Richard Feynmann and Albert Einstein would be examples of geniuses who were extremely strong mathematically while being relatively weak verbally. More commonly, though, purely intellectual abilities tend to be uniformly high or uniformly low in a given individual, leading to the concept of an underlying "g" or "general intelligence" that powers all the specialized intellectual aptitudes. Still, this doesn't happen with everyone, and the exceptions, like Richard Feynmann and Albert Einstein, are very important. Tests like the Wechsler Adult Intelligence Scale (WAIS) consist of a number of subtests that are scored separately and can measure the profile for an individual. (Dr. Howard Gardner has defined seven types of intelligence, while Dr. Robert Sternberg has identified three.)
It's also easier to make an IQ score that's lower than your true IQ than it is to make a score that's higher. Taking a test on a bad day, or spending too much time on a few difficult items could artificially lower one's score. The best results are obtained when more than one test is administered.
What Does Adult IQ Mean?
Generally, one's mental age stops rising rapidly when one reaches the latter teens--e. g., 16. Consequently, on some IQ tests, "16" was taken as the chronological-age divisor in an IQ calculation for adults. The Wechsler Adult Intelligence Scale is calibrated for all ages up to 70, with chronological-age divisors appropriate to every age 70 or below.
The average IQ is, by definition, 100. To get an idea what this means, someone with an IQ of 80 or below is considered to be marginally able to cope with the adult world. People with IQ's of 80 or below typically work as unskilled laborers such as lawn maintenance and trash pickup. They generally need help from friends or family to manage life's complications. About 10% of the population has an IQ of 80 or below.
People with IQ's of 80-90 are a little on the slow side but may be found in fast-food restaurants, day-care centers, etc. They may also be found in unskilled jobs. About 16% of the population has IQ's in this range.
People with IQ's of 90-110 generally occupy semi-skilled positions, including typists, receptionists, assembly line workers, and checkout clerks. They are able to keep up with the world, and comprise about 46% of the public.
People with IQ's in the 110 to 120 range fill the skilled trades and include some tool and die makers, teachers, and Ph. D.'s among their ranks. They also make up 16% of the population.
People with IQ's of 120 and above tend to staff the professions as doctors, dentists, lawyers, teachers, and college professors. They fall in the upper 10% of the population.
The average IQ of all college professors is 130, which lies within the upper 3% of the general public.