3. Examine the output file. There are lots of interesting bits of information there. You can see the a and b parameters for each item. Be aware that the column that has the c parameter should be ignored at this point. This program uses c to signify a different value than what we typically think of as the guessing parameter. That value, when you estimate the 3-PL model, will be signified with the letter g for IRTPro. Notice which items are most discriminating (large values of a ) and which items are relatively easy and relatively difficult. From this output file, if you click on the “Analysis” tab this time, you will see a “Graphics” command. Click on that, and you will see the IRFs for each item. (See Figure 20.3e ).