plotTCC {GGUM}

Plot test characteristic curve (TCC)

Description

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

Usage

plotTCC(IP, Th)

Arguments

IP

Object of class GGUM.

Th

Theta estimates from function Theta.EAP().

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.

Details

This function plots the test characteristic curve (TCC).

Author(s)

Jorge N. Tendeiro, [e-mail]

Examples

## Not run: 
# 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)

## End(Not run)
## Not run: 
# 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)

## End(Not run)