ABSTRACT
Item banks can provide a valuable resource for Diagnostic Assessment, but if they are to be exploited successfully people must understand how an item bank measures attainment. To understand the nature of assessment in education it helps to consider other familiar kinds of measurement, and temperature, in Centigrade or Fahrenheit, provides the best analogy. The credibility of each measurement they make should be considered as important as the reliability and validity of the test we use to make it. Such information might best be described as semi-diagnostic since it can at best identify problems but not explain them. First they must understand the meaning of the simple scale. Then they must realize the significance of this in terms of the curriculum of teaching and learning. Finally they must learn how best to react when the simple picture does not fit for a particular student or class, in order to provide for each of them the best learning environment they can.
