Openirt 2pl

[Andrew Marty]

Hi. I am using openirt to calculate traits and item characteristics. I need the calculations in 2pl - the default for openirt is 3pl. My syntax is:
openirt, model ("2pl") id(portalid) save_item_parameters("items.dta") save_trait_parameters("traits.dta") item_prefix("q")
The problem is that the results are produced in 3pl. The syntax runs without error messages. How can I make openirt produce 2pl results?

[Erik Ruzek]

I am not sure, and it doesn't look like openirt has been updated in some time according to the github page. Does your Stata version have the now built-in irt suite? You can also use gsem for this. The other option is to use Bartosz Kondratek uirt command, which is very flexible and has a thorough and useful Stata Journal article associated with it. Note that 2pl is the default in uirt. All these will provide you the item and trait data you want.

[Andrew Marty]

Thanks Erik. Yes, my version of STATA has the built-in IRT module. The problem is that it can't produce EAP estimates or parameters, which we need. I will certainly follow up UIRT. I have seen other references to GSEM - haven't figured out how to use it for IRT yet.