Like other aspects of setting tests, equating begins with collecting the data. Generally four designs are used to
collect the data: (a) single-group design, (b) equivalent-groups, and (c) anchor-test design (d) Common–Person
Design. In single-group design two or more forms of test are presented to the same group of testinees. The
advantage of this design is that the errors of measuring will be reduced. The reason of this reduction is that just one
group of testinees enter in the equating process of test. Therefore, the differences between tests cannot be confused
with those between the groups. Since in this design it is necessary to testinees to response the items of several tests,
fatigue is a basic problem, especially when physical and intellectual activities are included. The effect of exercise is
another problem that should be considered. If awareness of a test improves testining performance, so the test that is
to be presented later would seem easier. In order to avoid fatigue and the effects of exercise, some kinds of spiraling
process should be used. For example, succession of presenting the forms of tests can work as a modifying factor