Educational measurement is the assigning of numerals to traits such as achievement, interest, attitudes, aptitudes, intelligence and performance.
In terms of the broad body of purely mathematical theory drawn on, there is substantial overlap between educational measurement and psychometrics.
However, certain approaches considered to be a part of psychometrics, including Classical test theory, Item Response Theory and the Rasch model, were originally developed more specifically for the analysis of data from educational assessments.
[2][3] One of the aims of applying theory and techniques in educational measurement is to try to place the results of different tests administered to different groups of students on a single or common scale through processes known as test equating.
The rationale is that because different assessments usually have different difficulties, the total scores cannot be directly compared.