# Chapter 5 Item selection

The most important feature to select items for an instrument is the item information, and ultimately the test information. In chapter @(ch:information), the interpretation of information by $$D$$-score and age is described. For the development of a test instrument it is important that the items in the test provide information over the entire range of $$D$$-scores. The more information there is at a particular $$D$$-score range, the more precise the scores around that range can best estimated with the test.

Besides considering the information in the test. The following features can help, to make the test as representative and useful as possible for the study purpose.