To calibrate these items, they had been administered to a pre-testing sample of 3000 candidates. These candidates represented the Dutch labor force. Each of the candidates answered a subset of items in the bank. Bilog MG (ZIMOWSKI
et al.,1996) had been applied to calibrate the items with the 2PLM. The curves of the most informative and second most informative items for every ability level are shown in Figure 1.