\name{Tucker}
\alias{Tucker}
\docType{data}
\title{
9 Cognitive variables discussed by Tucker and Lewis (1973)
}
\description{Tucker and Lewis (1973) introduced a reliability coefficient for ML factor analysis.  Their example data set was previously reported by Tucker (1958) and taken from Thurstone and Thurstone (1941).  The correlation matrix is a 9 x 9 for 710 subjects and has two correlated factors of ability: Word Fluency and Verbal.
}
\usage{data(Tucker)}
\format{
  A data frame with 9 observations on the following 9 variables.
  \describe{
    \item{\code{t42}}{Prefixes}
    \item{\code{t54}}{Suffixes}
    \item{\code{t45}}{Chicago Reading Test: Vocabulary}
    \item{\code{t46}}{Chicago Reading Test: Sentences}
    \item{\code{t23}}{First and last letters}
    \item{\code{t24}}{First letters}
    \item{\code{t27}}{Four letter words}
    \item{\code{t10}}{Completion}
    \item{\code{t51}}{Same or Opposite}
  }
}
\details{The correlation matrix from Tucker (1958) was used in Tucker and Lewis (1973) for the Tucker-Lewis Index of factoring reliability.
}
\source{
Tucker, Ledyard (1958) An inter-battery method of factor analysis, Psychometrika, 23, 111-136.
	

}
\references{
L.~Tucker and C.~Lewis. (1973) A reliability coefficient for maximum likelihood factor analysis.
 Psychometrika, 38(1):1--10.


F.~J. Floyd and K.~F. Widaman. (1995)  Factor analysis in the development and refinement of clinical
  assessment instruments., Psychological Assessment, 7(3):286 -- 299.

}
\examples{
data(Tucker)
fa(Tucker,2,n.obs=710)
omega(Tucker,2)
}
\keyword{datasets}