plotevenlope: Confidence bands

In SICSresearch/IRTpp: Estimating IRT Parameters using the IRT Methodology

Description

Graphic bands of confidence of an item, to evaluate the goodness of fit of the model.

Usage

plotenvelope(item, numboot, alpha, model, data)

Arguments

item	a number indicating the item that you want evaluate.
numboot	number of iterations bootstrap, used to plot the envelopes.
alpha	level of significance to plot the envelopes.
model	object irtpp() type.
data	the data frame or a matrix with the test data.

Value

plot with the envelopes and the caracteristic curve of the item.

Author(s)

SICS Research, National University of Colombia [e-mail]

References

David Thissen, Howard Wainer D. (1990). Confidence Envelopes for Item Response Theory. Journal of Educational Statistics, Vol 15, No 2, 113-128.

See Also

orlando_itemf, z3_itemf

Examples

#Simulates a test and returns a list:
test <- simulateTest()

#the simulated data:
t_data <- test$test

#model:
mod <- irtpp(dataset = t_data,model = "3PL")

#Envelopes:
item <- 8
numboot <- 100
alpha <- 0.05

#call the function:
plotenvelope(item=item,numboot=numboot,alpha=alpha,model=mod,data=t_data)

SICSresearch/IRTpp documentation built on May 9, 2019, 11:11 a.m.