\HeaderA{ability.cov}{Ability and Intelligence Tests}{ability.cov}
\keyword{datasets}{ability.cov}
\begin{Description}\relax
Six tests were given to 112 individuals. The covariance matrix is
given in this object.
\end{Description}
\begin{Usage}
\begin{verbatim}ability.cov\end{verbatim}
\end{Usage}
\begin{Details}\relax
The tests are described as
\describe{
\item[general:] a non-verbal measure of general intelligence using
Cattell's culture-fair test.
\item[picture:] a picture-completion test
\item[blocks:] block design
\item[maze:] mazes
\item[reading:] reading comprehension
\item[vocab:] vocabulary
}

Bartholomew gives both covariance and correlation matrices,
but these are inconsistent.  Neither are in the original paper.
\end{Details}
\begin{Source}\relax
Barthlomew, D. J. (1987) \emph{Latent Variable Analysis and Factor
Analysis.} Griffin.  

Barthlomew, D. J.  and Knott, M. (1990) \emph{Latent Variable Analysis
and Factor Analysis.} Second Edition, Arnold.
\end{Source}
\begin{References}\relax
Smith, G. A. and Stanley G. (1983)
Clocking \eqn{g}{}: relating intelligence and measures of timed
performance. \emph{Intelligence}, \bold{7}, 353--368.
\end{References}
\begin{Examples}
\begin{ExampleCode}
require(stats)
(ability.FA <- factanal(factors = 1, covmat=ability.cov))
update(ability.FA, factors=2)
update(ability.FA, factors=2, rotation="promax")
\end{ExampleCode}
\end{Examples}

