Determinants of artificial DIF : a study based on simulated polytomous data

• A general problem in DIF analyses is that some items favouring one group can induce the appear-ance of DIF in others favouring the other group. Artificial DIF is used as a concept for describing and explaining that kind of DIF which is an artefact of the procedure for identifying DIF, con-trasting it to real DIF which is inherent to an item.  The purpose of this paper is to elucidate how real both uniform and non-uniform DIF, referenced to the expected value curve, induce artificial DIF, how this DIF impacts on the person parameter estimates and how different factors affect real and artificial DIF, in particular the alignment of person and item locations. The results show that the same basic principles apply to non-uniform DIF as to uniform DIF, but that the effects on person measurement are less pronounced in non-uniform DIF. Similar to artifi-cial DIF induced by real uniform DIF, the size of artificial DIF is determined by the magnitude of the real non-uniform DIF. In addition, in both uniform and non-uniform DIF, the magnitude of artificial DIF depends on the location of the items relative to the distribution of the persons. In contrast to uniform DIF, the direction of non-uniform real DIF (e.g. favouring one group or the other) is affected by the location of the items relative to the distribution of the persons.The results of the simulation study also confirm that regardless of type of DIF, in the person estimates, artifi-cial DIF never balances out real DIF. 

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Public Health, Global Health, Social Medicine and Epidemiology (hsv//eng)

Nyckelord

differential item functioning

uniform

non-uniform

artificial

Rasch models

Public Health Science

Folkhälsovetenskap

Statistics

Statistik

Publikations- och innehållstyp

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