model_3pl: 3-parameter-logistic model

In xluo11/Rirt: Data Analysis and Parameter Estimation Using Item Response Theory

Description

Common computations and operations for the 3PL model

Usage

model_3pl_prob(t, a, b, c, D = 1.702)

model_3pl_info(t, a, b, c, D = 1.702)

model_3pl_lh(u, t, a, b, c, D = 1.702, log = FALSE)

model_3pl_rescale(t, a, b, c, scale = c("t", "b"), mean = 0, sd = 1)

model_3pl_gendata(n_p, n_i, t = NULL, a = NULL, b = NULL, c = NULL,
  D = 1.702, t_dist = c(0, 1), a_dist = c(-0.1, 0.2), b_dist = c(0,
  0.7), c_dist = c(5, 46), t_bounds = c(-3, 3), a_bounds = c(0.01,
  2.5), b_bounds = c(-3, 3), c_bounds = c(0, 0.5), missing = NULL,
  ...)

model_3pl_plot(a, b, c, D = 1.702, type = c("prob", "info"),
  total = FALSE, xaxis = seq(-4, 4, 0.1))

model_3pl_plot_loglh(u, a, b, c, D = 1.702, xaxis = seq(-4, 4, 0.1),
  verbose = FALSE)

Arguments

t	ability parameters, 1d vector
a	discrimination parameters, 1d vector
b	difficulty parameters, 1d vector
c	guessing parameters, 1d vector
D	the scaling constant, default=1.702
u	observed responses, 2d matrix
log	True to return log-likelihood
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
n_p	the number of people to be generated
n_i	the number of items to be generated
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
c_dist	parameters of the beta distribution used to generate c-parameters
t_bounds	bounds of the ability parameters
a_bounds	bounds of the discrimination parameters
b_bounds	bounds of the difficulty parameters
c_bounds	bounds of the guessing parameters
missing	the proportion or number of missing responses
...	additional arguments
type	the type of plot: 'prob' for item characteristic curve (ICC) and 'info' for item information function curve (IIFC)
total	TRUE to sum values over items
xaxis	the values of x-axis
verbose	TRUE to print rough maximum likelihood estimates

Value

model_3pl_prob returns the resulting probabilities in a matrix

model_3pl_info returns the resulting information in a matrix

model_3pl_lh returns the resulting likelihood in a matrix

model_3pl_rescale returns t, a, b, c parameters on the new scale

model_3pl_gendata returns the generated response matrix and parameters in a list

model_3pl_plot returns a ggplot object

model_3pl_plot_loglh returns a ggplot object

Examples

with(model_3pl_gendata(10, 5), model_3pl_prob(t, a, b, c))
with(model_3pl_gendata(10, 5), model_3pl_info(t, a, b, c))
with(model_3pl_gendata(10, 5), model_3pl_lh(u, t, a, b, c))
model_3pl_gendata(10, 5)
model_3pl_gendata(10, 5, a=1, c=0, missing=.1)
with(model_3pl_gendata(10, 5), model_3pl_plot(a, b, c, type="prob"))
with(model_3pl_gendata(10, 5), model_3pl_plot(a, b, c, type="info", total=TRUE))
with(model_3pl_gendata(5, 50), model_3pl_plot_loglh(u, a, b, c))

xluo11/Rirt documentation built on Nov. 5, 2019, 12:29 p.m.