Question about Mixture of rating scales

[shentong]

Hi folks,

I have a 30-item instrument with two subscales(18 items in the confidence scale and 12 items in the anxiety scale). The responses is a five-point likert scale. Both of the two subscales are developed based on the Rasch rating scale model, so instead of using a multidimensional partial credit model, I decided to run the mixture of two rating scales multidimensional model.  I created the design matrix and conquest command file based on the example given in the Conquest Mannual P122-129.  However,  the analysis output did not show the item dififculty and SE  estimates of the last item in each subscale and the step parameter of the last step for each subscale. That is to say, it only showed the 17 item parameter estimates and 3 step parameters for the confidence scale, and 11 item parameters and 3 step parameters for the anxiety scale.

I'm wondering if there is a way to let Conquest display the parameter estimates of all 30 items and 8 steps? Or did I make a mistake about my design matrix? Any help will be greatly appreciated!

Thanks!

Tong

[Alvin Vista]

This may be due to having the constraints set to items. Change your constrains to cases instead if you want all item parameters displayed.

[shentong]

Hey, thanks for your reply!

Yes, I set the constraints to items, because I want to compare the conquest results with Winsteps results which constrains the item difficulty mean to zero. But when I run other uni- and multi-dimensional models with constraints set to items, Conquest still presents the item difficulty estimates and SEs that are constrained.

So, with "set constraints=items", is there a way to let the all item parameters displayed?

Thanks,
Tong

[Alvin Vista]

try a reset all;
Then run your syntax again.
If it still is not producing what you have in mind, can you send to us with your dataset?

[shentong]

Yes, sure! What is your email address? I tried to attach the data and syntax with this message but couldn't succeed...

Thanks!

Tong

[Alvin Vista]

alvin.vista@acer.edu.au