Test development is an extensive and time-consuming process. It includes (a) establishing the purpose of a test, (b) defining the construct of interest, (c) drafting test items, (d) conducting a pilot test, and (e) analyzing item response data. These steps are cyclical in that the analysis of item response data leads to the identification of good items and informs revision of bad ones. Revised items are then subjected to additional rounds of pilot testing and analysis. Several authors provide detailed information about each of these steps (see Crocker & Algina, 1986), but the analysis of item response data is the focus of this and many other chapters in this book. It is an important step in the development of quality measures.