ConQuest Community

Help desk => Questions and Answers => Topic started by: Juliane B. on March 16, 2021, 10:07:27 AM

Title: Obtain Fit Statistics Like in Quest
Post by: Juliane B. on March 16, 2021, 10:07:27 AM
Hey,

my colleagues and I are used to working with the old Acer Quest software. I have tried to switch to ConQuest, because I need ability estimates for some zero and perfect scores in my data set (Quest cannot calculate them). Unfortunately, none of us have found a way to receive the same fit statistics in ConQuest easily provided by Quest:
Is it possible to obtain these values using ConQuest, and if yes, how?

Thanks a lot in advance!
Juliane
Title: Re: Obtain Fit Statistics Like in Quest
Post by: dan_c on March 16, 2021, 10:18:05 AM
check out the output of the commands show and fit.

https://conquestmanual.acer.org/s4-00.html#show (https://conquestmanual.acer.org/s4-00.html#show)

Quote
tables =value list
If parameters output is requested, a total of eleven different tables can be produced.
...

The contents of the tables are:
...

2. The estimates, errors and fit statistics for each of the parameters in the item response model.
...
4.7.54.4 Examples

Code: [Select]
show;Produces displays with default settings and writes them to the output window.



https://conquestmanual.acer.org/s4-00.html#fit (https://conquestmanual.acer.org/s4-00.html#fit)

Quote
Produces residual-based fit statistics.
...
4.7.25.4 Examples

Code: [Select]
fit >> fit.res;Uses the default fit design matrix and writes results to the file fit.res.


Title: Re: Obtain Fit Statistics Like in Quest
Post by: Juliane B. on April 09, 2021, 02:50:38 PM
Dear Dan,

Thanks a lot for your fast reply!
The show command does provide me with all the parameter estimates I am looking for.
Unfortunately, I still cannot find the overall case estimates I need (a summary of case estimates - mean and SD; Overall fit statistics for the case estimates - Infit MNSQ and SD, Infit t Mean and SD). Is it possible to have these provided by conquest (as in quest) or do they need to be calculated by hand?
I am also wondering about the individual case fit values printed via pfit. Do these fit statistics represent the infit t value or do they represent the unweighted fit statistic?

Thank you very much.

Best,
Juliane
Title: Re: Obtain Fit Statistics Like in Quest
Post by: dan_c on April 12, 2021, 09:02:40 AM
Hi Juliane,

in the show file you find the output from the population model which includes regression output and the latent variance-covariaince matrix (both unconditional, conditional and model R square if you include regressors in the population model). This is where you will find the mean and variance of the latent ability distribution. See e.g.:

Code: [Select]
REGRESSION COEFFICIENTS

Regression Variable

CONSTANT                   1.332 ( 0.115)
-----------------------------------------------
An asterisk next to a parameter estimate indicates that it is constrained
===============================================

UNCONDITIONAL COVARIANCE/CORRELATION MATRIX

Dimension

Dimension_1
-------------------------------------------
Variance                   0.625  ( 0.113)
-------------------------------------------
An asterisk next to a parameter estimate indicates that it is constrained
The person fit statistics in pfit are weighted mean squares/infit statistics with expectation 1.