Y. Kim et Pa. Pilkonis, Selecting the most informative items in the IIP scales for personality disorders: An application of item response theory, J PERS DIS, 13(2), 1999, pp. 157-174
The first goal of the present analyses was to shorten the five scales (Pilk
onis, P, A., Kim, Y,, Proietti, J, M,, & Barkham, M, [1996], Journal of Per
sonality Disorders, 10, 355-369) for personality disorders (PDs) developed
from the Inventory of Interpersonal Problems (IIP), thereby increasing thei
r attractiveness for screening purposes. The second goal was to illustrate,
for more general purposes, the utility of item response theory (IRT) for s
uch scale refinement. IRT analyses were performed using data collected from
six different samples (N = 1149) at five sites and a two-parameter (2P) gr
aded model designed for multiple response items like those on the IIP, The
five most informative items from each scale were identified, based on the m
agnitude of item discrimination parameters and the range and elevation of i
ndividual item information functions. Preliminary analyses of the reliabili
ty and validity of the short forms of the scales (totaling 25 items) suppor
ted their value as alternatives to the longer forms (consisting of 47 items
), although definitive tests of their psychometric properties await crossva
lidation in independent samples. Analyses of the quality receiver operating
characteristics (QROC) of the long and short forms showed that both versio
ns can be useful in predicting the presence versus absence of any PD diagno
sis arrived at by using either a "best estimate" clinical consensus method
or a structured Axis II interview.