mteb/BrightProPsychologyRetrieval huggingface dataset:
Non-shared family environment and environment outside the family  

Although parents treat their children differently, such differential treatment
explains only a small amount of nonshared environmental influence. One
suggestion is that children react differently to the same environment because
of different genes. More likely influences may be the impact of peers and
other experiences outside the family.  [15]  [121]
In a  normal distribution  , data are symmetrically distributed with no skew. Most values
cluster around a central region, with values tapering off as they go further
away from the center.
##  What is the standard normal distribution?
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An **intelligence quotient** ( **IQ** ) is a total score derived from a set of
 standardised tests  or
subtests designed to assess  human intelligence  .  [1]  The abbreviation "IQ" was coined by the 
psychologist   William Stern
 "William Stern \(psychologist\)") for
the  German  term
_Intelligenzquotient_ , his term for a scoring method for  intelligence
 tests at  University of Breslau
 he advocated in a
1912 book.  [2]

Historically, IQ was a score obtained by dividing a person's  mental age
 score, obtained by administering an
intelligence test, by the person's chronological age, both expressed in terms
of years and months. The resulting fraction (  quotient  ) was multiplied by 100 to obtain the IQ score.  [3]  For modern
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fairness of IQ tests when used in South Africa.  [101]  [102]  Standard
intelligence tests, such as the Stanford–Binet, are often inappropriate for 
autistic  children; the alternative of using
developmental or adaptive skills measures are relatively poor measures of
intelligence in autistic children, and may have resulted in incorrect claims
that a majority of autistic children are of low intelligence.  [103]
Reliability  

IQ scores can differ to some degree for the same person on different IQ tests,
so a person does not always belong to the same IQ score range each time the
person is tested. (IQ score table data and pupil pseudonyms adapted from
description of KABC-II norming study cited in  Kaufman (2009)  .  [82]  [83]
)  Pupil  |  KABC-II  |  WISC-III  |  WJ-III
---|---|---|---
A  |  90  |  95  |  111
B  |  125  |  110  |  105
C  |  100  |  93  |  101
D  |  116  |  127  |  118
E  |  93  |  105  |  93
F  |  106  |  105  |  105
G  |  95  |  100  |  90
H  |  112  |  113  |  103
I  |  104  |  96  |  97
J  |  101  |  99  |  86
K  |  81  |  78  |  75
L  |  116  |  124  |  102

Psychometricians generally regard IQ tests as having high  statistical
reliability  "Reliability
\(psychometrics\)") .  [15]  [84]  Reliability represents the measurement
consistency of a test.  [85]  A reliable test produces similar scores upon
repetition.  [85]  On aggregate, IQ tests exhibit high reliability, although
test-takers may have varying scores when taking the same test on differing
occasions, and may have varying scores when taking different IQ tests at the
**__ Statistics **
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The  **standard normal distribution**
 , also
called the **_z_ -distribution ** , is a special normal distribution where the
mean is 0 and the standard deviation is 1.
Group differences  

Among the most controversial issues related to the study of intelligence is
the observation that IQ scores vary on average between ethnic and racial
groups, though these differences have fluctuated and in many cases steadily
decreased over time.  [183]  While there is little scholarly debate about the
continued existence of some of these differences, the current scientific
consensus is that they stem from environmental rather than genetic causes.
[184]  [185]  [186]  The existence of differences in IQ between the sexes has
been debated, and largely depends on which tests are performed.  [187]  [188]
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Psychological_traits "Correlates of crime") was
−0.2. This association is generally regarded as small and prone to
disappearance or a substantial reduction after controlling for the proper
covariates, being much smaller than typical sociological correlates.  [170]
It was −0.19 between IQ scores and the number of juvenile offenses in a large
Danish sample; with social class controlled for, the correlation dropped to
−0.17. A correlation of 0.20 means that the  explained variance
 accounts for 4% of the total
variance. The causal links between psychometric ability and social outcomes
may be indirect. Children with poor scholastic performance may feel alienated.
Consequently, they may be more likely to engage in delinquent behavior,
compared to other children who do well.  [15]

In his book _ The g Factor
 _ (1998),  Arthur Jensen  cited data which showed that, regardless of race, people with IQs
between 70 and 90 have higher crime rates than people with IQs below or above
this range, with the peak range being between 80 and 90.

The 2009 _Handbook of Crime Correlates_ stated that reviews have found that
around eight IQ points, or 0.5 SD, separate criminals from the general
population, especially for persistent serious offenders. It has been suggested
that this simply reflects that "only dumb ones get caught" but there is
similarly a negative relation between IQ and self-reported offending. That
children with  conduct disorder 
have lower IQ than their peers "strongly argues" for the theory.  [171]

A study of the relationship between US county-level IQ and US county-level
crime rates found that higher average IQs were very weakly associated with
Race  

Main article:  Race and intelligence 

While the concept of "  race  "Race
\(human categorization\)") " is a  social construct
 ,  [189]  discussions
of a purported relationship between race and intelligence, as well as claims
of genetic differences in intelligence along racial lines, have appeared in
both  popular science  and 
academic research  since the
modern concept of race was first introduced. Despite the tremendous amount of
research done on the topic, no scientific evidence has emerged that the
average IQ scores of different population groups can be attributed to genetic
differences between those groups.  [190]  [191]  [192]  Growing evidence
indicates that environmental factors, not genetic ones, explain the racial IQ
gap.  [193]  [194]  [186]

A 1996 task force investigation on intelligence sponsored by the  American
Psychological Association  concluded that there were significant variations
in IQ across races.  [15]  However, a systematic analysis by  William Dickens
 and  James Flynn
 "James Flynn \(academic\)") (2006) showed the
gap between black and white Americans to have closed dramatically during the
period between 1972 and 2002, suggesting that, in their words, the "constancy
of the Black–White IQ gap is a myth".  [195]
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Flynn effect  

Main article:  Flynn effect 

Since the early 20th century, raw scores on IQ tests have increased in most
parts of the world.  [104]  [105]  [106]  When a new version of an IQ test is
normed, the standard scoring is set so performance at the population median
results in a score of IQ 100. The phenomenon of rising raw score performance
means if test-takers are scored by a constant standard scoring rule, IQ test
scores have been rising at an average rate of around three IQ points per
decade. This phenomenon was named the Flynn effect in the book _ The Bell
Curve  _ after  James R. Flynn
 "Jim Flynn \(academic\)") , the author who did
the most to bring this phenomenon to the attention of psychologists.  [107]
[108]

Researchers have been exploring the issue of whether the Flynn effect is
equally strong on performance of all kinds of IQ test items, whether the
effect may have ended in some developed nations, whether there are social
subgroup differences in the effect, and what possible causes of the effect
might be.  [109]  A 2011 textbook, _IQ and Human Intelligence_ , by  N. J.
Mackintosh  , noted the
Flynn effect demolishes the fears that IQ would be decreased. He also asks
whether it represents a real increase in intelligence beyond IQ scores.  [110]
A 2011 psychology textbook, lead authored by Harvard Psychologist Professor 
Daniel Schacter  , noted that
humans' inherited intelligence could be  going down  while acquired intelligence goes up.  [111]
###  Grammar Checker
Genetics and environment  

 Environmental  "Environment
\(biophysical\)") and  genetic  factors play a
role in determining IQ. Their relative importance has been the subject of much
research and debate.  [116]
See also  

*  Emotional competence 
*  Emotional intelligence (EI)  , also known as emotional quotient (EQ) and emotional intelligence quotient (EIQ)
*  Raven's Progressive Matrices 
*  Stanford–Binet Intelligence Scales 
*  Wechsler Adult Intelligence Scale 
*  Woodcock–Johnson Tests of Cognitive Abilities
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Concepts
If your data truly are not normal, many analyses have non-parametric
alternatives, such as the one-way ANOVA analog,  Kruskal-Wallis
 , and the two-sample t test analog,  Mann-Whitney
 . These methods don’t rely on an assumption of
normality. The downside is that they generally also  have less power

, so it’s harder to detect statistical differences. Here are some
recommendations to  determine when to use nonparametric tests

.
same age. Like all statistical quantities, any particular estimate of IQ has
an associated standard error that measures uncertainty about the estimate. For
modern tests, the confidence interval can be approximately 10 points and
reported  standard error of measurement  can be as low as about three points.  [86]
Reported standard error may be an underestimate, as it does not account for
all sources of error.  [87]

Outside influences such as low motivation or high anxiety can occasionally
lower a person's IQ test score.  [85]  For individuals with very low scores,
the 95% confidence interval may be greater than 40 points, potentially
complicating the accuracy of diagnoses of intellectual disability.  [88]  By
the same token, high IQ scores are also significantly less reliable than those
near to the population median.  [89]  Reports of IQ scores much higher than
160 are considered dubious.  [90]
Along these same lines, critics such as  Keith Stanovich
 do not dispute the capacity of IQ
test scores to predict some kinds of achievement, but argue that basing a
concept of intelligence on IQ test scores alone neglects other important
aspects of mental ability.  [15]  [95]   Robert Sternberg
 , another significant critic of
IQ as the main measure of human cognitive abilities, argued that reducing the
concept of intelligence to the measure of _g_ does not fully account for the
different skills and knowledge types that produce success in human society.
[96]

Despite these objections, clinical psychologists generally regard IQ scores as
having sufficient  statistical validity 
"Validity \(statistics\)") for many clinical purposes.  [ _ specify
 _ ]  [30]  [97]
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The  standard normal distribution
 , also
called the _z_ -distribution, is a special  normal distribution
 where the  mean
 is 0 and the  standard deviation
 is 1.
If that does not fit with your intuition, remember that the null hypothesis
for these tests is that your sample came from a normally distributed
population of data. So as with any significant test result, you are rejecting
the idea that the data was normally distributed. See our guide for more
specific information and background on  interpreting normality test p-values

.
Individual genes  

A very large proportion of the over 17,000 human genes are thought to have an
effect on the development and functionality of the brain.  [123]  While a
number of individual genes have been reported to be associated with IQ, none
have a strong effect. Deary and colleagues (2009) reported that no finding of
a strong single gene effect on IQ has been replicated.  [124]  Recent findings
of gene associations with normally varying intellectual differences in adults
and children continue to show weak effects for any one gene.  [125]  [126]

A 2017  meta-analysis  conducted on
approximately 78,000 subjects identified 52 genes associated with
intelligence.  [127]   FNBP1L  is reported to be the
single gene most associated with both adult and child intelligence.  [128]
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John B. Carroll  (1993),
after a comprehensive reanalysis of earlier data, proposed the  three stratum
theory  , which is a
hierarchical model with three levels. The bottom stratum consists of narrow
abilities that are highly specialized (e.g., induction, spelling ability). The
second stratum consists of broad abilities. Carroll identified eight second-
stratum abilities. Carroll accepted Spearman's concept of general
intelligence, for the most part, as a representation of the uppermost, third
stratum.  [55]  [56]

In 1999, a merging of the Gf-Gc theory of Cattell and Horn with Carroll's
Three-Stratum theory has led to the Cattell–Horn–Carroll theory (CHC Theory),
with _g_ as the top of the hierarchy, ten broad abilities below, and further
subdivided into seventy narrow abilities on the third stratum. CHC Theory has
greatly influenced many of the current broad IQ tests.  [30]

Modern tests do not necessarily measure all of these broad abilities. For
example, _quantitative knowledge_ and _reading & writing ability _ may be seen
as measures of school achievement and not IQ.  [30]  _Decision speed_ may be
difficult to measure without special equipment. _g_ was earlier often
subdivided into only Gf and Gc, which were thought to correspond to the
nonverbal or performance subtests and verbal subtests in earlier versions of
the popular Wechsler IQ test. More recent research has shown the situation to
be more complex.  [30]  Modern comprehensive IQ tests do not stop at reporting
a single IQ score. Although they still give an overall score, they now also
give scores for many of these more restricted abilities, identifying
particular strengths and weaknesses of an individual.  [30]
Following the empirical rule:
](https://www.scribbr.com/plagiarism-
checker/?scr_source=knowledgebase&scr_medium=sidebar&scr_campaign=minimalistic-
sidebar) [
##  Empirical rule
Figure 1: Probability density curve
of normal distribution
](https://www.scribbr.com/ai-
proofreader/?scr_source=knowledgebase&scr_medium=sidebar&scr_campaign=minimalistic-
sidebar) [
Ellis Island ](/wiki/Ellis_Island "Ellis Island") , 1914) and to a court of
law (1914).  [48]

Unlike Galton, who promoted eugenics through selective breeding for positive
traits, Goddard went with the US eugenics movement to eliminate "undesirable"
traits.  [49]  Goddard used the term "  feeble-minded  " to refer to people who did not perform well on the test. He
argued that "feeble-mindedness" was caused by heredity, and thus feeble-minded
people should be prevented from giving birth, either by institutional
isolation or sterilization surgeries.  [48]  At first, sterilization targeted
the disabled, but was later extended to poor people. Goddard's intelligence
test was endorsed by the eugenicists to push for laws for forced
sterilization. Different states adopted the sterilization laws at different
paces. These laws, whose constitutionality was upheld by the Supreme Court in
their 1927 ruling  Buck v. Bell  , forced
over 60,000 people to go through sterilization in the United States.  [50]

California's sterilization program was so effective that the Nazis turned to
the government for advice on how to prevent the birth of the "unfit".  [51]
While the US eugenics movement lost much of its momentum in the 1940s in view
of the horrors of Nazi Germany, advocates of eugenics (including Nazi
geneticist  Otmar Freiherr von Verschuer  ) continued to work and promote their ideas in
the United States.  [51]  In later decades, some eugenic principles have made
a resurgence as a voluntary means of selective reproduction, with some calling
them "  new eugenics  ".  [52]  As it
becomes possible to test for and correlate genes with IQ (and its proxies),
[53]  ethicists and embryonic  genetic testing  companies are attempting to understand the ways in which
the technology can be ethically deployed.  [54]
pending "All edits by unregistered and new
users are subject to review prior to becoming visible to unregistered users")

From Wikipedia, the free encyclopedia

This is the  latest accepted revision  ,  reviewed

on _23 March 2024_ .

Score from a test designed to assess intelligence

"IQ" redirects here. For other uses, see  IQ (disambiguation)
 "IQ \(disambiguation\)") .

Intelligence quotient
---
[ ![\[picture of an example IQ test
item\]](//upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Raven_Matrix.svg/290px-
Raven_Matrix.svg.png) ](/wiki/File:Raven_Matrix.svg)

One kind of IQ test item, modelled after items in the  Raven's Progressive
Matrices  test

 ICD-10-PCS  |  [ Z01.8 ](https://icd.who.int/browse10/2019/en
History  

See also:  History of the race and intelligence controversy
The  central limit theorem  is the basis for how normal distributions work in statistics.
Age  

IQ can change to some degree over the course of childhood.  [113]  In one 
longitudinal study  , the mean
IQ scores of tests at ages 17 and 18 were correlated at  _r_ = 0.86  with the
mean scores of tests at ages five, six, and seven and at  _r_ = 0.96  [ _
further explanation needed   _ ]  with the mean scores of tests at ages 11, 12, and 13.  [15]

For decades, practitioners' handbooks and textbooks on IQ testing have
reported IQ declines with age after the beginning of adulthood. However, later
researchers pointed out this phenomenon is related to the  Flynn effect
 and is in part a  cohort
 "Cohort \(statistics\)") effect rather than a
true aging effect. A variety of studies of IQ and aging have been conducted
since the norming of the first Wechsler Intelligence Scale drew attention to
IQ differences in different age groups of adults. The current consensus is
that  fluid intelligence 
generally declines with age after early adulthood, while  crystallized
intelligence 
remains intact. Both cohort effects (the birth year of the test-takers) and
practice effects (test-takers taking the same form of IQ test more than once)
must be controlled to gain accurate data.  [ _ inconsistent
 _ ]  It is unclear whether any
lifestyle intervention can preserve fluid intelligence into older ages.  [114]

The exact peak age of fluid intelligence or crystallized intelligence remains
elusive. Cross-sectional studies usually show that especially fluid
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Job performance  

According to Schmidt and Hunter, "for hiring employees without previous
experience in the job the most valid predictor of future performance is
general mental ability."  [20]  The validity of IQ as a predictor of  job
performance  is above zero for all
work studied to date, but varies with the type of job and across different
studies, ranging from 0.2 to 0.6.  [155]  The correlations were higher when
the unreliability of measurement methods was controlled for.  [15]  While IQ
is more strongly correlated with reasoning and less so with motor function,
[156]  IQ-test scores predict performance ratings in all occupations.  [20]

That said, for highly qualified activities (research, management) low IQ
scores are more likely to be a barrier to adequate performance, whereas for
minimally-skilled activities, athletic strength (manual strength, speed,
stamina, and coordination) is more likely to influence performance.  [20]  The
prevailing view among academics is that it is largely through the quicker
acquisition of job-relevant knowledge that higher IQ mediates job performance.
This view has been challenged by Byington & Felps (2010), who argued that "the
current applications of IQ-reflective tests allow individuals with high IQ
scores to receive greater access to developmental resources, enabling them to
acquire additional capabilities over time, and ultimately perform their jobs
better."  [157]

Newer studies find that the effects of IQ on job performance have been greatly
overestimated. The current estimates of the correlation between job
performance and IQ are about 0.23 correcting for unreliability and range
restriction.  [158]  [159]
##  Why do normal distributions matter?
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There are many statistical tests to evaluate normality, although we don’t
recommend  relying on them blindly

. Prism offers  four normality test options

: D'Agostino-Pearson, Anderson-Darling, Shapiro-Wilk and Kolmogorov-Smirnov.
Each of the tests produces a p-value that tests the null hypothesis that the
values (the sample) were sampled from a Normal (Gaussian) distribution (or
population). :
External links  

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**Intelligence quotient**

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 ** _ .

Look up _** IQer  **
_ or _** IQed  ** _
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