This specifies which facets are not to be centered. Centered facets are constrained to have a mean element measure of zero. In most analyses, if more than one facet is non-centered, the frame of reference is not sufficiently constrained and ambiguity results. The usual convention is to center the frame of reference on the agents of measurement: items, tasks, judges. This establishes the origin. Then the objects of measurement, persons, are positioned with respect to this origin.

 

If both Noncenter= and Center= are specified, only the first encountered is actioned.

 

When any element within a facet is anchored, or group anchored, then the origin of the scale for that facet is set by the anchoring, and that facet is automatically non-centered.

 

Example 1: Persons are facet 2 and are not to be centered, then

Noncenter=2

 

Example 2: Facet 1 contains the boys, and facet 3 the girls:

Noncenter=1,3

 

Example 3: All facets are anchored or centered or self-defined:

Noncenter= or Noncenter=0

 

Self-definition occurs when there is only one active facet so that the item difficulties are defined relative to an implicit origin, as in the "Three Mile" example.