An Item Response Theory Evaluation of an English Version of the Trier Personality Inventory (TPI)

The measurement equivalence of an English-language version of the Trier Personality Inventory (TPI) was evaluated, using statistical methods based on item response theory (IRT) to identity items that displayed differential item functioning (DIF). In Study 1, the TPI was administered to 295 American and 213 West German subjects. From among the 120 items tested, 11 DIF items were detected. A follow-up study using a new sample of 203 Americans was conducted to replicate the original study and to evaluate the post hoc explanation that translation error was the source of DIF for one item. DIF was replicated for 6 of the 11 DIF items found in Study 1, and DIF was eliminated for one item by retranslation. Overall, there was significant agreement between the DIF indexes found in Studies I and 2 for all 120 items analyzed. Some problems in replicating significant indexes of DIF are discussed.