[Rasch] Sample size?

Shirin Shirazi shirin.shirazi at gmail.com
Wed Sep 30 09:22:52 AEST 2015

My great appreciation for your informative responses.

I was just thinking about sort of quantitative analysis which puts a limit
not only on the number of items but gets to number of subjects on the basis
of the number of items using kind of formula saying that the iteration gets
nowhere if we have for example a 45 item questionnaire but just 30
respondents. Although, I did such a small scale study a few years ago with
one of my students and we got good results through running Factor analysis,
and at that time I thought that maybe it is because of the two issues:
raters and item traits. Any idea of yours is highly welcome.

Thanks Professor Commons and Professor Bonds for your great feedback


On Tue, Sep 29, 2015 at 11:36 PM, Bond, Trevor <trevor.bond at jcu.edu.au>

> Dear Shirin,
> The only issue is the density of the data.
> If both raters rate all persons on all items, the only issue will be that
> the no of responses in each category is likely be too small to estimate
> their difficulty.
> Mike uses the very small data set from Guilford as an example. I cover
> that example in Chap 8 as well. Pls take a look at it.
> Best
> Sent from 007's iPad
> > On 30 Sep 2015, at 12:32 AM, Shirin Shirazi <shirin.shirazi at gmail.com>
> wrote:
> >
> > Dear List Members,
> >
> > Good day. I have a question and I wonder if you can afford some time to
> read and respond. But please take it from a person who does not know the
> ropes of MFRM.
> >
> >  If we assume the model is item and sample independent, then does it
> matter if we have a very limited sample size with limited related facets to
> run Rasch model? I mean have the minimum and maximum number of facets
> (examinees, items, examiners, etc) been determined the violation of which
> hinders us from running the program. For example, two raters, 10 testees, a
> 15-item questionnaire?
> >
> > I would be mostly appreciative of your kind response to my question.
> >
> > Shirin Shirazi
> > PhD in Applied Linguistics
> > ________________________________________
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> > email: Rasch at acer.edu.au
> > web:
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