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Messages - dan_c

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The item response model fitted by ACER ConQuest is the multidimensional random coefficients multinomial logit model (MRCMLM). The parametrisation is presented in:

Adams, R.J., Wilson, M.R., and Wang, W.C. 1997. The multidimensional random coefficients multinomial logit. Applied Psychological Measurement, 21, 1–24.

See, the section describing he response probability model.

If you are using integer scoring, you can see both the item deltas and thresholds by using the command `itanal`.

Questions and Answers / Re: multidimensional run error
« on: February 28, 2019, 08:08:32 AM »
contact our sales team with details of your licence key purchase, and they can provide you with access to a beta version.

Questions and Answers / Re: multidimensional run error
« on: February 26, 2019, 09:42:27 AM »
about the version, here is what I got after typing 'conquest' and return (I am running it on Mac):
ConQuest build: Oct 3 2017
Standard Version

Your error message is likely a version issue. I can get this model to run, but i am still concerned about identification. I attach the output i get.

you can type the command `about` at the command line to get the version details:

Code: [Select]
On my machine, I am running the latest beta build and I get (please don't publish your key details - delete it from below):

< about;
Developed by
    Australian Council for Educational Research
    University of California, Berkeley

Your key: ...
Expires: ...

Professional Build:  Feb 22 2019
Version: 4.30.2

    Ray Adams, Margaret Wu, Greg Macaskill, Sam Haldane, Xiao Xun Sun, Dan Cloney

Questions and Answers / Re: multidimensional run error
« on: February 26, 2019, 12:44:58 AM »
Can you let us know what version of ConQuest you are running?

Can you upload your data and syntax file, or provide a minimum working example?

In general, I wonder if this model is identified? With an item constraint, the difficulty of one (the last) item within each dimension is constrained to be the negative sum of the other items. With only one item, you cannot impose this constraint. If you combine dimension 1 and 2 into a single dimension, this will probably run fine. Alternatively you will need to consider a different design/importing a design.

ConQuest News / Re: Documentation
« on: February 25, 2019, 10:53:22 AM »
We do not plan on providing a separate printed ConQuest 3.0 manual. All functionality as described in the v2.0 manual still holds.  For the additional functionality of ConQuest 3.0, the ConQuest 2 manual is supplemented by the ACER ConQuest 3.0 command reference and the notes and tutorials available from:

A ConQuest 5 manual is on the way.

Early versions will be available at

Feedback and comments welcome.

Questions and Answers / Re: Item Separation Index in ConQuest?
« on: February 21, 2019, 03:58:39 AM »
I would like to calculate the item separation index (G). ...
Is it possible to derive them from the item separation reliability?

Hi Urs,

ACER ConQuest doesn't produce an item separation index, but it is related to the item separation reliability.

Check out this link:

You can see here that the relationship between the separation reliability and index is given by:

Separation Ratio = G = (True SD)/(RMSE)

Separation Reliability = R = (True SD)^2/(Observed SD)^2

where (True SD)^2 = (Observed SD)^2 - (RMSE)^2

and therefore:

R = G^2/(1+G^2)

and with a bit of algebra, you can approximate G = sqrt(R/(1-R))

And if you compare with the reported values in the table in the link above, you can see it's pretty close:

RGG = sqrt(R/(1-R))

Questions and Answers / Re: Previous use: 2019 Month 3 Day 19
« on: February 19, 2019, 03:56:16 AM »
Please contact the ACER Shop customer service team:

You will need to re-authorise your install of ACER ConQuest.

ConQuest News / Re: Documentation
« on: December 21, 2018, 12:41:50 AM »
The Conquest Command Reference is undergoing an update.

Check out the beta build here:

Feedback and comments welcome.

Questions and Answers / Re: Chi-Square value for MH statistics
« on: November 16, 2018, 08:53:15 AM »
Hi all - this is a bug in the mh output of ConQuest. The output won't print CHISQ values > 10 (and instead will print "_BIG_"), but the value is being calculated and the associated output is correct.

Thank you to Moritz for providing a reproducible example to isolate it.

If this is an urgent issue for users, I can produce the correct output for you. We will push out a fix in the coming weeks.

Questions and Answers / Re: Chi-Square value for MH statistics
« on: November 14, 2018, 01:38:18 AM »

You can download version 4 from the website:

If you have purchased a Standard Licence, you can send the key (or your invoice) to the sales team and they will provide you with a new key to use with Version 4.

If the issue still persists, let me know.

Questions and Answers / Re: Chi-Square value for MH statistics
« on: November 12, 2018, 10:29:32 PM »
Hi Moritz,

Can you run:

Code: [Select]
at the console and let me know what version you are using? In more recent version of CQ, the actual value is reported.

Questions and Answers / Re: Item discrimination
« on: October 26, 2018, 11:12:19 AM »
Have a read of this paper:

There are also some new features for assessing fit using simulation in the next release of ConQuest - watch this space.

Questions and Answers / Re: problem with combined item difficulty map
« on: September 20, 2018, 12:49:00 AM »
check out the command reference:

Code: [Select]

If reply is yes, ability estimates (WLE, MLE, EAP and plausible values) will be generated after the model has converged. This may accelerate later commands that require the use or display of these estimates. The default is no.

If you add the option abilities=yes to your estimate statement, ConQuest will produce case estimates.

Alternatively you can request specific case estimates. Say you wanted to only estimate PVs and include them in the Combined Item Difficulty Map:

Code: [Select]
show ! estimates=latent, filetype = xlsx, tables = 1:2:3:4:5:9 >> myShow.xlsx;
For a list of the tables in show files, see the command ref.

Can you post your datafile, and syntax or create a reproducible example using the online examples so we can reproduce this?


Questions and Answers / Re: Item thresholds cannot be produced
« on: July 26, 2018, 02:38:25 AM »
Can you post your datafile, syntax file, and output, or create a reproducible example using the online examples?


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