Equating in item response theory 400px|Figure 1: Test characteristic curves showing the relationship between total score and person location for two different tests in relation to a common scale. In this example a total of 37 on Assessment 1 equates to a total of 34.9 on Assessment 2 as shown by the vertical line In item response theory, person locations are estimated on a scale; i.e.  locations are estimated in relation to a unit and origin. It is common in educational assessment to employ tests in order to assess different groups of students with the intention of establishing a common scale by equating the origins, and sometimes units, of the scales obtained from response data from the different tests. The process is referred to as equating or test equating.
Equating in item response theory 400px|Figure 1: Test characteristic curves showing the relationship between total score and person location for two different tests in relation to a common scale. In this example a total of 37 on Assessment 1 equates to a total of 34.9 on Assessment 2 as shown by the vertical line In item response theory, person "locations" (measures of some quality being assessed by a test) are estimated on an interval scale; i.e. , locations are estimated in relation to a unit and origin. It is common in educational assessment to employ tests in order to assess different groups of students with the intention of establishing a common scale by equating the origins, and when appropriate also the units, of the scales obtained from response data from the different tests. The process is referred to as equating or test equating.
R
locations
"locations" (measures of some quality being assessed by a test)
R
a
an interval
A
,
R
sometimes
when appropriate also the