DIF (Differential Item Functioning)

Differential Item Functioning (DIF) occurs when individuals from different groups (such as different genders, ethnicities, or backgrounds) with the same underlying ability or trait have different chances of answering a test question correctly. In other words, the question might be biased or unfair if it favors one group over another, not because of true differences in the measured trait but due to how the question is worded or structured. Detecting DIF helps ensure tests are fair and truly measure what they’re intended to across diverse groups.