#' Piston Rings Data Set.
#' 
#' The Piston Rings data set was taken from Montgomery's book. It consists of
#' 40 samples of size 5 each of values of the diameter of the piston rings.
#' 
#' 
#' @name pistonrings
#' @docType data
#' @format A data frame with 40 observations on the following 5 variables.
#' \describe{ 
#' \item{V1}{The fisrt measure.} 
#' \item{V2}{The second measure.} 
#' \item{V3}{The third measure.} 
#' \item{V4}{The fouth measure.} 
#' \item{V5}{The fifth measure.} }
#' @source Montgomery, D.C.,(2008)."Introduction to Statistical Quality
#' Control".4th Ed. Wiley
#' @examples
#' 
#' data(pistonrings)
#' 
NULL