prior distribution of parameter Theta and some other questions.

[Can Yang]

Hi there.

1. How can I make parameter theta follow a prior distribution (like Mnorm) when I deal with empirical data(need to estimate students' multidimension abilities)? It seems that mirt.model() doesn't work (can only set prior distributions of parameter a,d,g,u).

2. Can I save values of parameter a',d etc.(after runing mirt() ) as  R variables for subsequent calculations? 

3. The method of estimating theta values (in MIRT model) is using fscores()?

Thank you.

[Phil Chalmers]

On Tue, Nov 21, 2017 at 2:59 AM, Can Yang <2525...@qq.com> wrote:

Hi there.

1. How can I make parameter theta follow a prior distribution (like Mnorm) when I deal with empirical data(need to estimate students' multidimension abilities)? It seems that mirt.model() doesn't work (can only set prior distributions of parameter a,d,g,u).

The default prior is for all thetas to follow a multivariate normal. You can change this, but it requites defining your own probability density function via createGroup(). But I would generally advise against doing so. 

 

2. Can I save values of parameter a',d etc.(after runing mirt() ) as  R variables for subsequent calculations? 

coef() and mod2values()

 

3. The method of estimating theta values (in MIRT model) is using fscores()?

Yes. 

Phil

 

Thank you.

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