Confidence bands

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Description

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

Usage

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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 ammontenegrod@unal.edu.co

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

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#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)

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