Equating test scores for different forms of the same exam using IRT

[Nahla Betelmal]

Hi Everyone,

I wonder if there are some commands in Stata that I can use to equate test scores for different exam forms . It seems that there are three known methods to equate scores using IRT :

1. Conversion
2. Concurrent Calibration
3. Fixed Anchor Calibration

There is a commercial software called Xcalibre (link below) that performs IRT equating and I hope that Stata has similar facility. I did some search , but I could not find the commands to do such equating in Stata, I would highly appreciate it if someone can show me how or where to find the Stata commands for IRT equating if there are any or if there is an alternative way, please.

http://www.assess.com/three-ways-to-...ating-linking/

Thank you
Kind regard
Nahla

[wbuchanan]

Nahla ,

As a quick reminder, community members are strongly encouraged to use their full real names.

There are certainly more than 3 equating methodologies around. There is a set of programs written in C that was written by/with Brennan and Kolen at the University of Iowa. jMetrik is an open source program written in Java that includes several equating methods.

This isnt something that is currently supported directly in Stata with any packages that I am aware of. A large part of the methodological choice is also dependent on your sampling methodology. Providing some information about your sampling methods may lead to other responses that you might find more helpful/useful.

[Nahla Betelmal]

Hi

Thank you for your reply. I contacted the helpdesk regarding my full name.

Now, I found two Stata user-written commands by Leah McGuire. Thank you Leah!

The first one is 'LINEQUATE' which computes equating constants to perform linear equating of two versions of a test using an anchor test. linequate from http://fmwww.bc.edu/RePEc/bocode/l

The second one is 'MEQUATE' which performs and Item Response Theory equating method using common items. mequate from http://fmwww.bc.edu/RePEc/bocode/m

I have not tried running these commands myself yet but plan to do so soon and see how it goes.

Now regarding other packages, R does the IRT equating beautifully. Have a look at : https://cran.r-project.org/web/packa.../equateIRT.pdf published March,30, 2017

Hope someone finds this helpful

Thank you
Kind regards
Nahla Betelmal