model_grm: Graded Response Model

In Rirt: Data Analysis and Parameter Estimation Using Item Response Theory

Description

Common computations and operations for the GRM

Usage

model_grm_prob(t, a, b, D = 1.702, raw = FALSE)

model_grm_info(t, a, b, D = 1.702)

model_grm_lh(u, t, a, b, D = 1.702, log = FALSE)

model_grm_gendata(n_p, n_i, n_c, t = NULL, a = NULL, b = NULL,
  D = 1.702, t_dist = c(0, 1), a_dist = c(-0.1, 0.2), b_dist = c(0,
  0.8), t_bounds = c(-3, 3), a_bounds = c(0.01, 2.5),
  b_bounds = c(-3, 3), missing = NULL, ...)

model_grm_rescale(t, a, b, scale = c("t", "b"), mean = 0, sd = 1)

model_grm_plot(a, b, D = 1.702, type = c("prob", "info"),
  item_level = FALSE, total = FALSE, xaxis = seq(-6, 6, 0.1),
  raw = FALSE)

model_grm_plot_loglh(u, a, b, D = 1.702, xaxis = seq(-6, 6, 0.1),
  verbose = FALSE)

Arguments

t	ability parameters, 1d vector
a	discrimination parameters, 1d vector
b	item location parameters, 2d matrix
D	the scaling constant, default=1.702
raw	TRUE to return P*
u	observed scores (starting from 0), 2d matrix
log	TRUE to return log-likelihood
n_p	the number of people to be generated
n_i	the number of items to be generated
n_c	the number of score categories
t_dist	parameters of the normal distribution used to generate t-parameters
a_dist	parameters of the lognormal distribution used to generate a-parameters
b_dist	parameters of the normal distribution used to generate b-parameters
t_bounds	the bounds of the ability parameters
a_bounds	the bounds of the discrimination parameters
b_bounds	the bounds of the difficulty parameters
missing	the proportion or number of missing responses
...	additional arguments
scale	the scale, 't' for theta or 'b' for b-parameters
mean	the mean of the new scale
sd	the standard deviation of the new scale
type	the type of plot, prob for ICC and info for IIFC
item_level	TRUE to combine categories
total	TRUE to sum values over items
xaxis	the values of x-axis
verbose	TRUE to print rough maximum likelihood values

Value

model_grm_prob returns the resulting probabilities in a 3d array

model_grm_info returns the resulting information in a 3d array

model_grm_lh returns the resulting likelihood in a matrix

model_grm_gendata returns the generated response data and parameters in a list

model_grm_rescale returns t, a, b parameters on the new scale

model_grm_plot returns a ggplot object

model_grm_plot_loglh returns a ggplot object

Examples

with(model_grm_gendata(10, 5, 3), model_grm_prob(t, a, b))
with(model_grm_gendata(10, 5, 3), model_grm_info(t, a, b))
with(model_grm_gendata(10, 5, 3), model_grm_lh(u, t, a, b))
model_grm_gendata(10, 5, 3)
model_grm_gendata(10, 5, 3, missing=.1)
with(model_grm_gendata(10, 5, 3), model_grm_plot(a, b, type='prob'))
with(model_grm_gendata(10, 5, 3), model_grm_plot(a, b, type='info', item_level=TRUE))
with(model_grm_gendata(5, 50, 3), model_grm_plot_loglh(u, a, b))

Rirt documentation built on Oct. 30, 2019, 12:13 p.m.