5.2 Preferred variant

The D-score can be measures with items from many different instruments that all were designed to measure early child development. Inevitably, these instruments have many overlapping items between them. This was very useful to align the instruments in order to develop the D-score (see dbook II). Of course, the overlapping items are close, but not exactly the same. So for selecting items in preparation of an instrument to measure D-score, the preferred version of the item should be selected.