[DDI-users] Variable representation

[Rémi Dewitte]

Mary,

Thanks for your kind reply.

I find the pragmatic answer from Nesstar developer not really satisfactory
IMHO in the sense that DDI is not about "storing variables in a system
independent way" but as I understood so far a way to express things.

>From a question with 8 choices where you can pick 2 of them, I see at least
two ways of storing the result :
 - have 8 slots and code 0 or 1 if code is mentioned
 - have 2 stots with codes mentionned (you can have also some order with
this).

You have to make an early choice between 2 or 8 variables. I would argue
that it is a store (physical) matter and I don't want this detail to appear
at the logical layer. If the CodeScheme changes, it also changes the
variable scheme. Dealing with 8 variables is ok but when starting to have
few questions with between 20 to 40 codes as a multichoice, it becomes a
pain.

On the other side, I also understand that in the PhysicalStructure you have
to find a way to express how multi choice is handled. Which is not the
direction taken by DDI so far.

I hope my thoughts make sense.

Best regards,
Rémi

On Wed, Apr 15, 2009 at 13:24, Mary Vardigan <vardigan at umich.edu> wrote:

>  Remi,
>
>
>
> Regarding the multiple choice issue, I asked one of the original developers
> of Nesstar about this because I recalled that it came up. Here is what he
> said:
>
>
>
> “I remember that we were looking for an elegant  DDI-solution for this,
> but we did not find one. It is really tricky as the only system independent
> way of storing multiple choice variables is as a group of individual
> variables. In fact what we did in Nesstar was to use the  variable group
> element as a container and one of the alternatives of the variable group
> type attribute to indicate that this was a multiple response group.”
>
>
>
> Hope this is helpful.
>
>
>
> Regards,
>
> Mary
>
>
>
>
>
> *From:* ddi-users-bounces at icpsr.umich.edu [mailto:
> ddi-users-bounces at icpsr.umich.edu] *On Behalf Of *Rémi Dewitte
> *Sent:* Wednesday, April 15, 2009 5:56 AM
> *To:* ddi-users at icpsr.umich.edu
> *Subject:* [DDI-users] Variable representation
>
>
>
> Hello,
>
> I am going on working with DDI and here some of the questions I raised.
>
> It is common for a numeric variable, say body height for a respondent, to
> also have some non-response codes defined. NumericRepresentationType does
> not allow to reference a code scheme. Where to write these codes ?
>
> In our surveys, we have some "multichoice" questions, where do we write
> using DDI that the variable can have more than one values ? Sometimes the
> values are ordered, is there a place to say this ?
>
> Thanks a lot,
>
> Rémi
>
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>
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