The following step was the analysis of the displacement values of the common items between the third and fourth grade test forms.
The values of the common items, also known as anchor items, are crucial to align the metrics from different test forms, in order to compare scores.
By using this model, both sets of supplemental items were successfully linked to the common items, allowing the placement of all items on the same underlying measure of ability.
Based on this recalibration of the TRC-n-3, displacement estimates were analyzed to evaluate the stability of the common items' difficulty between the second and the third grade test forms.
Based on this recalibration of the TRC-e-3, displacement estimates were analyzed to evaluate the stability of the common items' difficulty between the second and the third grade test forms.
To evaluate the stability of the common items' difficulty between adjacent grades, displacement measures should be estimated for each anchor item to check discrepancies between the anchor value and the parameter that would have been estimated for the target test form if this parameter was unanchored (Linacre, 2011).
The common items between the LRR and protein kinase results were collected.
Kolen emphasises in particular, that, "for this design to work well, the common items need to represent the content and statistical characteristics of the total test" (p.20).
In order to address this limitation we compared results of follow-up I in the in-charges' control group with the needs assessment results on the common items.
The common items have identical definitions, observation time frames, and response codes and make these instruments an ideal tool to compare characteristics of older adults across settings [ 13].
Once the common items and concepts were identified, and their comparability assessed at follow-up, item scores could be standardized in the baseline cohorts to provide a common metric.
