% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/ctt.R
\name{ctt_table}
\alias{ctt_table}
\title{Traditional (classical test theory) statistics}
\usage{
ctt_table(fit)
}
\arguments{
\item{fit}{A fitted object from \code{\link{rasch}}.}
}
\value{
A list of class \code{"rasch_ctt"}: the per-item \code{table}
  (\code{item}, \code{n}, \code{min}, \code{max}, \code{facility},
  \code{item_total}, \code{item_rest}, \code{di}, \code{alpha_drop}), and
  the scalars
  \code{alpha}, \code{n} (complete cases), \code{mean}, \code{sd}, and
  \code{sem}.
}
\description{
The classical companion table conventionally reported alongside a Rasch
analysis (Andrich and Marais 2019, chs. 3-5), on complete cases only: per item the facility (mean score over
maximum), the item-total and corrected item-rest correlations, the
discrimination index DI = PRU - PRL (mean proportion-of-maximum in the
upper third of total scores minus the lower third), and alpha if the
item is deleted; plus coefficient alpha, the raw-score mean, SD, and the
classical standard error of measurement \eqn{s\sqrt{1 - \alpha}}, which
unlike the Rasch SE is one value for all persons.
}
\examples{
set.seed(1)
d <- seq(-2, 2, length.out = 8)
X <- matrix(rbinom(400 * 8, 1, plogis(outer(rnorm(400), d, "-"))), 400, 8)
colnames(X) <- paste0("I", 1:8)
ctt_table(rasch(X))
}
