icrfPN {lazy.irt}

R Documentation

Calculation of Item Response Function of Partial Credit Items
in Nominal Model Format

Description

Calculation of Item Response Function of Partial Credit Items
in Nominal Model Format

Usage

icrfPN(paramPN, theta, smallP = 0, print = 0, plot = 0, debug = 0)

Arguments

paramPN	Item Parameter Data Frame of Partial Credit Items in Nominal format
theta	Discrete theta values
smallP	Minimum value of probability
print	= 1 to print result
plot	= 1 to plot result
debug	= 1 to print intemediate result

Details

An Example of Item Parameter datastet: maxncat = 5
Note that the subscript of the b-parameter ranges between
1 and ncat-1 (= maxscore) (We set c0=0.)

ncat A b1 b2 b3 b4

Item1 2 1.0 0.0 . . .
Item2 2 1.0 0.0 . . .
Item3 3 1.5 -1.0 0.0 . .
Item4 4 1.5 -1.0 0.0 1.0 .
Item5 5 1.5 -1.0 0.0 1.0 2.0

ICRF of category k of item j at theta, namely, p_{jk}(theta)
is defined as
p_{jk}(theta) = Ez_{jk}(theta) / sum_{k=0}^{ncat[j]-1} Ez_{jk}(theta)
where
Ez_{jk}(theta) = exp( 1.7 z_{jk}(theta) )
and
z_{jk}(theta) = a_j k (theta - b_{k}), k=0,1, ..., ncat[j]-1
with b_{j0}=0.

Value

A list of:
P length(theta) x sum(ncat) icrf matrix
PP length(theta) x sum(ncat) icbf matrix
Pt length(theta) x nitems item response function

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