Analyzing the Effects of Heredity and Environment on IQ: A Statistical Examination of Identical Twins Raised Apart
Examination of genetic vs. environmental influences on intelligence.
Violet Stevens
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Analyzing the Effects of Heredity and Environment on IQ: A Statistical
Examination of Identical Twins Raised Apart
Effects of Heredity and Environment on IQ: In studying the effects of heredity and
environment on intelligence, it has been helpful to analyze the IQs of identical twins who were
separated soon after birth. Identical twins share identical genes. By studying identical twins
raised apart, we can eliminate the variable of heredity and better isolate the effects of the
environment. The accompanying table shows the IQs of pairs of identical twins (older twins are
x) raised apart (based on data from “IQs of Identical Twins Reared Apart,” by Arthur Jensen,
Behavioral Genetics). The sample data given here are typical of those obtained from other
studies.
a. Find the mean and standard deviation of the sample of older twins.
b. Find the mean and standard deviation of the sample of younger twins.
C. Based on the results from parts (a) and (b), does there appear to be a difference between the
means of the two populations? In exploring the association between IQs of twins, is such a
comparison of the two samples means the best approach? Why or why not?
d. Combine all of the sample IQ scores, then use a 0.05 significance level to test the claim that
the mean IQ score of twins reared apart is different from the mean IQ of 100.
e. Is there an association between IQs of twins who were separated soon after birth?
What method did you use? Write a summary statement about the effect of heredity and
environment on intelligence, and note that your conclusions will be based on this relatively small
sample of 12 pairs of identical twins.
x 107 96 103 90 96 113 86 99 109 105 96 89
y 111 97 116 107 99 111 85 108 102 105 100 93
There are different kinds of measures to measure the intelligence of an individual. The most
important one is the IQ. And it is the most commonly and widely used measure of intelligence
thus many researches have been done to check how to influence this value.
In this section we are considering the IQs of identical twins who were separated soon after birth
and using the statistical methods to analyze this data.
The older twins are represented as X in the data and younger ones by Y.
The obtained descriptive statistics is given below,
Examination of Identical Twins Raised Apart
Effects of Heredity and Environment on IQ: In studying the effects of heredity and
environment on intelligence, it has been helpful to analyze the IQs of identical twins who were
separated soon after birth. Identical twins share identical genes. By studying identical twins
raised apart, we can eliminate the variable of heredity and better isolate the effects of the
environment. The accompanying table shows the IQs of pairs of identical twins (older twins are
x) raised apart (based on data from “IQs of Identical Twins Reared Apart,” by Arthur Jensen,
Behavioral Genetics). The sample data given here are typical of those obtained from other
studies.
a. Find the mean and standard deviation of the sample of older twins.
b. Find the mean and standard deviation of the sample of younger twins.
C. Based on the results from parts (a) and (b), does there appear to be a difference between the
means of the two populations? In exploring the association between IQs of twins, is such a
comparison of the two samples means the best approach? Why or why not?
d. Combine all of the sample IQ scores, then use a 0.05 significance level to test the claim that
the mean IQ score of twins reared apart is different from the mean IQ of 100.
e. Is there an association between IQs of twins who were separated soon after birth?
What method did you use? Write a summary statement about the effect of heredity and
environment on intelligence, and note that your conclusions will be based on this relatively small
sample of 12 pairs of identical twins.
x 107 96 103 90 96 113 86 99 109 105 96 89
y 111 97 116 107 99 111 85 108 102 105 100 93
There are different kinds of measures to measure the intelligence of an individual. The most
important one is the IQ. And it is the most commonly and widely used measure of intelligence
thus many researches have been done to check how to influence this value.
In this section we are considering the IQs of identical twins who were separated soon after birth
and using the statistical methods to analyze this data.
The older twins are represented as X in the data and younger ones by Y.
The obtained descriptive statistics is given below,
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Subject
Psychology