Thus each student's initial ability estimate is the mean item difficulty. The first item a student sees is selected at random from those near 0.5 logits less than the initial estimated ability. Randomizing item selection improves test security by preventing students from experiencing similar tests.
Randomization also equalizes bank item use.
After the student responds to the first item, a revised competency measure and standard error are estimated. Again, an item is chosen from those near 0.5 logits easier than the estimated competency. After the student responds, the competency measure is again revised and a further item selected and administered. This process continues. This will reduce the size of the change in the ability estimate, preventing early nervousness or luck from distorting the test.