#' Triplets of Pairwise Comparisons
#'
#' @description
#' A synthetic forced-choice data set containing pairwise comparison responses
#' for the first 200 of 2000 participants on four triplets. The data were
#' originally generated as part of Brown and Maydeu-Olivares (2012) and are
#' distributed in the published R package \pkg{thurstonianIRT}.
#'
#' In each triplet, participants ranked three alternative statements according
#' to their preference. The rankings were then converted into dichotomous
#' pairwise responses for all three within-triplet comparisons.
#'
#' @format A data frame with 200 rows and 12 integer columns. Values are 0/1
#'   pairwise preference indicators. Overall, the 12 statements measure three
#'   traits. Items 1, 4, 7, and 10 load on trait 1; items 2, 5, 8, and 11 load
#'   on trait 2; and items 3, 6, 9, and 12 load on trait 3. Items 4, 9, and 11
#'   are reverse-keyed.
#' \describe{
#'   \item{i1i2}{Response preference between item 1 and item 2.}
#'   \item{i1i3}{Response preference between item 1 and item 3.}
#'   \item{i2i3}{Response preference between item 2 and item 3.}
#'   \item{i4i5}{Response preference between item 4 and item 5.}
#'   \item{i4i6}{Response preference between item 4 and item 6.}
#'   \item{i5i6}{Response preference between item 5 and item 6.}
#'   \item{i7i8}{Response preference between item 7 and item 8.}
#'   \item{i7i9}{Response preference between item 7 and item 9.}
#'   \item{i8i9}{Response preference between item 8 and item 9.}
#'   \item{i10i11}{Response preference between item 10 and item 11.}
#'   \item{i10i12}{Response preference between item 10 and item 12.}
#'   \item{i11i12}{Response preference between item 11 and item 12.}
#' }
#'
#' @source
#' Brown, A. & Maydeu-Olivares, A. (2012). Fitting a Thurstonian IRT model to
#' forced-choice data using Mplus. Behavior Research Methods, 44, 1135-1147.
#' doi:10.3758/s13428-012-0217-x
#'
#' The data file was taken from the published R package \pkg{thurstonianIRT}.
#'
#' @examples
#' data("triplets")
#' dim(triplets)
#' head(triplets)
#'
#' @docType data
#' @keywords datasets
#' @name triplets
NULL
