| PackageDescription | This data package contains the Item Response Theory (IRT) parameters
for the National Center for Education Statistics (NCES) items used on
the National Assessment of Education Progress (NAEP) from 1990 to 2015.
The values in these tables are used along with NAEP data to turn
student item responses into scores and include information about item
difficulty, discrimination, and guessing parameter for 3 parameter
logit (3PL) items. Parameters for Generalized Partial Credit Model
(GPCM) items are also included. The adjustments table contains the
information regarding the treatment of items (e.g., deletion of an item
or a collapsing of response categories), when these items did not
appear to fit the item response models used to describe the NAEP data.
Transformation constants change the score estimates that are obtained
from the IRT scaling program to the NAEP reporting metric. Values from
the years 2000 - 2013 were taken from the NCES website
<https://nces.ed.gov/nationsreportcard/> and values from 1990 - 1998
and 2015 were extracted from their NAEP data files. All subtest names
were reduced and homogenized to one word (e.g. "Reading to gain
information" became "information"). The various subtest names for
univariate transformation constants were all homogenized to
"univariate". |