icrfPN0 {lazy.irt}

R Documentation

Calculation of Partial Credit ICRF in Nominal format

Description

Calculation of Partial Credit ICRF in Nominal format

Usage

icrfPN0(param, theta, smallP = 0, print = 0, plot = 0, debug = 0)

Arguments

param	Item Parameter Data Frame
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 c-parameter ranges between
1 and ncat-1 (= maxscore) (We set c0=0.)

ncat A c1 c2 c3 c4

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( z_{jk}(theta) )
and
z_{jk}(theta) = a_j k theta + c_{k}, k=0,1, ..., ncat[j]-1
with c_{j0}=0.

Value

A list of
P length(theta) x sum(ncat) ICRF matrix
PP length(theta) x sum(ncat) ICBRF matrix
Pt length(theta) x nitems item response function
fromP, toP indexes of each ICRF in P
fromPP, toPP indexes of each ICBRF in PP

---