The Burt
data frame has 27 rows and 4 columns.
The ``data'' were simply (and notoriously) manufactured. The
same data are in the dataset ``twins" in the alr3
package, but with different labels.
Burt
This data frame contains the following columns:
IQ of twin raised by biological parents
IQ of twin raised by foster parents
A factor with levels (note: out of order):
high
;
low
;
medium
.