This function performs a so-called graphical model check on the basis of the previously performed Likelihood Ratio Test [tmt::tmt_lrttest()]. The estimated item parameters of the two groups are plotted against each other. There is the possibility in this function to highlight items, to be excluded items from the plot, and to produce confidence-ellipses if desired.
tmt_gmc(
object,
title = "graphical model check",
xaxis = NULL,
yaxis = NULL,
lim = NULL,
ellipse = FALSE,
drop = NULL,
alpha = 0.05,
legendtitle = "split criteria",
info = NULL
)object of the function [tmt::tmt_lrttest()]
of the plot
description of the x-axis
description of the y-axis
of the plot
should confidence-ellipse be plotted
which items should be excluded from the plot
which alpha should be used for the ellipse
Title of the Legend
vector with further information for the Plot with names of submitted items
#############################################################################
# Example of Graphical Model Check
#############################################################################
items <- seq(-3,3,length.out = 16)
names(items) <- paste0("i",1:16)
persons = 500
dat <- tmt:::sim.rm(theta = persons, b = items, seed = 1234)
#> The specified seed will be used for the theta parameters
dat.rm <- tmt_rm(dat)
dat.lrt <- tmt_lrtest(dat.rm, split = "median")
info <- rep(c("group_a","group_b"),each = 8)
names(info) <- paste0("i",1:16)
drop <- c("i1","i18")
#library(ggplot2)
plot <- tmt_gmc(object = dat.lrt,
ellipse = TRUE,
info = info,
drop = drop,
title = "graphical model check",
alpha = 0.05,
legendtitle = "split criteria")