Extra parameter

Keith Lau

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May 14, 2016, 12:14:37 AM5/14/16

to mirt-package

Hi Phil,

Could I introduce an extra parameter that does not belong to item parameters and population parameters but used for parameter constraints? I mean, like Mplus, allowing an extra parameter in model constraint:

(Mplus syntax)

MODEL CONSTRAINT:
NEW(z); # an extra parameter
... # doing some parameter constraints with item parameters or population parameters

Of course, the "z" parameter is estimated. I wonder if it is possible by using alabama.

Thanks!

Phil Chalmers

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May 14, 2016, 7:41:49 PM5/14/16

to Keith Lau, mirt-package

Not sure I completely understand what you mean. What does this extra parameter do/what are you trying to use it for?

Phil

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Keith Lau

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May 15, 2016, 11:54:21 PM5/15/16

to mirt-package, genw...@gmail.com

Hi Phil,

Estimate correlation coefficient, but indirectly by using the z parameter (-∞< z < ∞) via Fisher transformation. So, the z parameter is an extra parameter.

Phil Chalmers於 2016年5月15日星期日 UTC+8上午7時41分49秒寫道：

Phil Chalmers

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May 19, 2016, 7:23:10 AM5/19/16

to Keith Lau, mirt-package

I see. I don't see an easy way to do this at the moment because the latent trait S4 class is designed to only support a standard MNV distribution. I suppose this could be modified sometime in the future though, but its currently not possible.

On Sunday, May 15, 2016, Keith Lau <genw...@gmail.com> wrote:

Hi Phil,

Estimate correlation coefficient, but indirectly by using the z parameter (-∞< z < ∞) via Fisher transformation. So, the z parameter is an extra parameter.

Phil Chalmers於 2016年5月15日星期日 UTC+8上午7時41分49秒寫道：
Not sure I completely understand what you mean. What does this extra parameter do/what are you trying to use it for?

Phil

On Sat, May 14, 2016 at 12:14 AM, Keith Lau <genw...@gmail.com> wrote:
Hi Phil,

Could I introduce an extra parameter that does not belong to item parameters and population parameters but used for parameter constraints? I mean, like Mplus, allowing an extra parameter in model constraint:

(Mplus syntax)

MODEL CONSTRAINT:
NEW(z); # an extra parameter
... # doing some parameter constraints with item parameters or population parameters

Of course, the "z" parameter is estimated. I wonder if it is possible by using alabama.

Thanks!

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