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Topics - gsbeglia

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Questions and Answers / equivalent analyses for Winsteps and Conquest
« on: January 05, 2018, 08:19:16 PM »
My lab is in the process of trying to move from Winsteps to Conquest and we need to make sure we are running equivalent analyses in the two programs. The first question I have is about the ICC figures, which have different x axis labels and look somewhat different in Winsteps and Conquest (I am unable to attach a document with ICC figures because of their size but the probabilities for selecting each answer option are somewhat different for the two programs). I want to determine if both programs have the same axes and can be interpreted the same way. The  x-axis in Conquest is "latent trait (logits)" and in Winsteps the x-axis is "person measure minus item measure".

The second question I have is about determining dif. Using these item*gender estimates in ConQuest, I would like to apply the same cutoffs for determining the presence of dif that we have historically used for Winsteps outputs. In a Winsteps dif analysis, there are estimates given for each gender that we then subtract from one another to determine the magnitude of dif between males and females. Are these Winsteps estimates equivalent to the item*gender estimate that ConQuest generates? If so, can I subtract the item*gender estimates in ConQuest to determine the magnitude of dif?


Questions and Answers / Three dimensional partial credit model won't run
« on: January 05, 2018, 04:14:20 AM »
Hi all. I'm trying to run a three dimensional between item partial credit model for a 24 item instrument on ConQuest4. I was able to run the one dimensional model but when I try to run the three dimensional model, it runs for several hours, generates the itn and wle files and then ConQuest crashes. This three dimensional model worked fine on our old version of ConQuest (version 1). The syntax is below and the data set is attached. Any help would be much appreciated.


datafile pre_test_121917.dat;
format pid 1-11 responses 14-37;
codes 1,2,3,4,5;
set constraints=cases, warnings=no;
score (1,2,3,4,5) (1,2,3,4,5) ()           ()          !items(1-8);
score (1,2,3,4,5)   ()        (1,2,3,4,5)  ()          !items(9-16);
score (1,2,3,4,5) ()         ()            (1,2,3,4,5) !items(17-24);
Model item + item*step;
export parameters            >> pre_121917_D3.prm;
export reg_coefficients      >> pre_121917_D3.reg;
export covariance            >> ipre_121917_D3.cov;
Estimate !method=montecarlo, nodes=2000, converge = .005;
itanal                       >> pre_121917_D3.itn;
show cases !estimate=wle     >> pre_121917_D3.wle;
show !estimate=latent        >> pre_121917_D3.shw;
equivalence wle           >> pre_equivalence_121917_D3.wle;
plot icc;

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