Effect of Transferring or Removing DIF (Differential Item Functioning)–Flagged Anchor Items on IRT (Item Response Theory) Equating

• In Event: AERA Roundtable Session Sunday 11:40 am Four Seasons Ballroom 1
  In Roundtable Session: Advances in Differential Item Functioning (DIF) Detection: Methods, Applications, and Implications (Table 12)

Abstract

Examining the presence of Differential Item Functioning (DIF) is one way to identify the validity of anchor items in the common-item nonequivalent group design. This study explores the effect of DIF flagged anchor items on IRT true and observed score equating. The simulated datasets were calibrated, and the IRT equating results were compared after detected DIF items were removed. The findings showed three DIF methods found similar flagged items, although the delta method showed more restricted results than Lord’s and Raju’s methods. The equating results were less likely to be affected by the flagged anchor items. This study implies that DIF analysis shed light on the validity of anchor items; however, IRT equating was similar regardless of DIF anchor items.

Authors

• Junhee Park, University of Iowa

• Jeongmin Ji, University of Iowa