st: New programs for differential item function (DIF) and for PARSCALE

[Laura Gibbons <gibbonsl@u.washington.edu>]

Thanks to Kit Baum, 4 new programs for detecting differential item 
function (DIF) and for interfacing with PARSCALE are downloadable from 
SSC.

Name: Difd
Title: Evaluates test items for differential item functioning (DIF).
Description:
    DIF detection is a first step in assessing bias in test items.
    Difd detects DIF in test items between groups, conditional on the
    trait that the test is measuring, using logistic regression.
    The criteria for DIF can be adjusted.  Continuous and multilevel
    'groups' are allowed.  In addition to logged results, DIFd.dta has
    results and some model-checking statistics.
Requires: Stata version 8.2

Name: DIFwithpar
Title: Detection of and adjustment for differential item functioning (DIF).
Description:
    Identifies differential item functioning, creates dummy/virtual items to
    be used to adjust ability (trait) estimates in PARSCALE, writes the code
    and data file needed to process the updated item list in PARSCALE, runs
    PARSCALE, and merges the ability estimates and standard errors into the
    original data set.
Requires: Stata version 8.2
Other programs needed: This program calls the PARSCALE program
    (www.ssicentral.com).

Name:  Runparscale
Title: Run PARSCALE from Stata
Description:
    Builds a PARSCALE data file and command file, executes the command file,
    displays the PARSCALE log file in Stata results window, and merges the
    PARSCALE theta estimates and their standard errors back into the
    original data set
Requires: Stata version 8.2
Other programs needed: This program calls the PARSCALE program
    (www.ssicentral.com).


Name:  Prepar
Title: Writes the code and data file needed to process variables in PARSCALE.
Description:
    This program writes the input code and data file for PARSCALE, which
    is a real time-saver if you aren't familiar with PARSCALE.
Requires: Stata version 8.0 (can be adapted to 7.0; see program)
Other programs needed: This program calls the PARSCALE program
    (www.ssicentral.com).

-Laura Gibbons
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Laura E. Gibbons, PhD
General Internal Medicine, University of Washington
Box 359780
Harborview Medical Center
325 Ninth Avenue, Seattle, WA  98104

phone: 206-744-1842   fax: 206-744-9917
Office address: 401 Broadway, Suite 5122
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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