D1. IRT Models questions

BILOG questions

Q1. I have trouble formatting my BILOG syntax. What should I do?

A1: At IRT\Estimating Parameters (1PL, 2PL, and.ppt, we provided a sample BILOG syntax and a brief description for each command. Mistakes are more likely to happen when the syntax doesn't read like "English" to you. For instance, in the tutorial, we used the first four characters as the Subject ID, followed by Responses from the first item. If your dataset is formatted differently, the numbers in the line ">INPUT SAMPLE=99999; (4A1,10A1)" have to be changed accordingly.

Q2. My BILOG run does not provide meaningful outputs like you provided on the tutorial. What should I do?

A2: At IRT\Estimating Parameters (1PL, 2PL, and.ppt, we have suggested that you may want to look at .ph1, .ph2, and .ph3 output files. For instance, you have to make sure that BILOG reads the dataset correctly and the statistics are reasonable (.ph1), and the estimation procedure converged (.ph2).

Q3. Do I need to provide a title or comments in my BILOG syntax?

A3: It's up to you. Providing title and comment may help you identify which dataset you are running.

Q4. Do I have to use file extensions like .3PL, .PAR, etc.?

A4: You may use any file extensions you want. We used those special file extensions such that it will be easier to tell the content of the file. In addition, any text editor such as Notepad provided by Windows can read those text files easily. Just remember that if you change your file extension, you may have to modify your syntax as well.