burt {SMPracticals}

IQs of identical twins

Description

These are said to be measurements of IQ scores for pairs of identical twins, the first raised by foster parents and the second raised by natural parents, published by Sir Cyril Burt. Cases are divided into groups according to parents' social class, A-C, labelled 1-3. The general objective is to assess the impact of social class, and in particular the effect of environment, on IQ.

Usage

data(burt)

Format

A data frame with 27 observations on the following 3 variables.

y

IQ score for twin raised in foster home

x

IQ score for twin raised by natural parents

class

Social class of twins

Details

Burt used these and similar data to argue that IQ was largely inherited, a view which strongly influenced British education through the creation of the 11+ exam, which was used to decide which children should be given different forms of education. However after his death it was suggested that the data were fake, a view accepted by some and strongly rebutted by others.

Source

Unpublished lecture notes of David Hinkley.

References

For information about Burt, see www.indiana.edu/~intell/burt.shtml

Examples

data(burt)
attach(burt)
par(pty="s")
plot(x,y,type="n",xlim=c(60,140),ylim=c(60,140))
text(x,y,class,cex=0.8)
abline(0,1,lty=2)