Item bias means that an item has different difficulty for the two groups and would suggest that items scale differently for the two groups.
If one item has different parameter values across groups, this is called differential item functioning (DIF) (Glas 1998, 2001; Speliotes et al. 2010).
A consequence of handling DIF in this way is that the resolved item has different parameter estimates for each group and is no longer invariant across the groups.
There may be practical applications of hierarchical scales, with items having different level of 'difficulty' in personality research.
We consider the case where a qualitatively homogeneous population of objects is tested by a set of non-destructive test items having different, but unknown beforehand levels of difficulty, and we need to evaluate/compare both the intrinsic abilities of these objects and the level of difficulty of the test items.
The mastication of food items having different physical properties, such as abrasiveness, toughness, hardness and brittleness, requires different masticatory processing [38] [43].
Item pairs could be unidominant, with both items having the same dominant modality (e.g., pink FLAMINGO and pink COTTON CANDY are both predominantly visual) or bidominant, with the two items having different dominant modalities (e.g., plain FABRIC and plain FOOD are predominantly visual and gustatory, respectively).
These phenomena were mainly due to the fact that the nine items have different pdf of MDCT coefficients.
When the items have different frequency distributions, Tabachnick and Fidell (2007) follow Comrey and Lee (1992) in suggesting using more stringent cutoffs going from 0.32 (poor), 0.45 (fair), 0.55 (good), 0.63 (very good), or 0.71 (excellent).
Items had different severity levels and pertained to 11 categories: thefts, alcohol and drugs consumption, verbal and physical aggression, possession of weapons, vandalism, truancy, driving without a license, assault, use of public transport without paying, lies and defiance of authority, and selling drugs.
