GGUM (version 0.5)

plotTCC: Plot test characteristic curve (TCC)

Description

plot.TCC plots the TCC for the GUM and the GGUM.

Usage

plotTCC(IP, Th)

Value

The function returns a list with three elements:

coords

(x, y) coordinates of the TCC.

cor.OBS.EXP

Correlation between observed and expected test scores (missing values pairwise removed).

cor.OBS.EXP.means

Correlation between observed and expected mean test scores (missing values pairwise removed). The \(\theta\) interval between \(-4\) through \(+4\) is divided in 100 subintervals of equal length. The observed and expected mean scores are computed for each subinterval.

Arguments

IP

Object of class GGUM.

Th

Theta estimates from function Theta.EAP().

Author

Jorge N. Tendeiro,

Details

This function plots the test characteristic curve (TCC).

Examples

if (FALSE) {
# For GUM:
# Generate data
#   (toy example: Too few items (due to computation time constraints) for 
#   accurate estimation of person parameters; larger number of items is 
#   required in practice):
gen1 <- GenData.GGUM(400, 5, 3, "GUM", seed = 139)
# Fit the GUM:
fit1 <- GUM(gen1$data, 3)
th1  <- Theta.EAP(fit1)
# Plot TCC:
plotTCC(fit1, th1)
}
if (FALSE) {
# For GGUM:
# Generate data:
set.seed(1); C <- sample(3:5, 10, replace = TRUE)
gen2 <- GenData.GGUM(2000, 10, C, "GGUM", seed = 156)
# Fit the GGUM:
fit2 <- GGUM(gen2$data, C)
th2  <- Theta.EAP(fit2)
# Plot TCC:
plotTCC(fit2, th2)
}