IRTpp (version 0.2.6.1)

orlando_itemf: Orlando's statistic

Description

Calculate the values of the statistics S_x2 from Maria Orlando and David Thisen.

Usage

orlando_itemf(patterns, G, zita, model)

Arguments

patterns

matrix of patterns response, the frequency of each pattern and the latent traits.

G

number of quadrature points.

zita

matrix of estimations of the parameters of the items (discrimination, difficulty, guessing).

model

type of model ( "1PL", 2PL", "3PL" ).

Value

Orlando's statistic, degrees of freedom and p-value for each item.

References

Orlando, M. & Thissen, D. (2000). Likelihood-based item fit indices for dichotomous item response theory models. Applied Psychological Measurement, 24, 50-64.

See Also

z3_itemf

Examples

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

#the simulated data:
data <- test$test

#model:
mod=irtpp(dataset = data,model = "3PL")

#Convert parameters to a matrix
zz <- parameter.matrix(mod$z,byrow = FALSE)

#Estimating Latent Traits
p_mat <- mod$prob_mat
trait <- individual.traits(model="3PL", itempars = zz,method = "EAP",dataset = data,
probability_matrix = p_mat)

#Z3 PERSONFIT-Statistic
orlando_itemf(patterns = as.matrix(trait),G = 61,zita = mod$z,model = "3PL")