[DDI-users] Variable representation

[Wendy Thomas]

Remi,

Basically the question focuses on how the data was captured while the 
logical product variable captures how it is expressed in the data file. My 
earlier email assumed a series of binary variables resulting from the 
multiple choice question. I suppose alternatively an array could be 
captured and would be treated as a single variable. The processing system 
would need to know how to handle that bundled array.

WEndy


On Wed, 15 Apr 2009, Rémi Dewitte wrote:

> 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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>> DDI-users at icpsr.umich.edu
>> http://www.icpsr.umich.edu/mailman/listinfo/ddi-users
>>
>>
>

Wendy L. Thomas                          Phone: +1 612.624.4389
Data Access Core Director		 Fax:   +1 612.626.8375
Minnesota Population Center              Email: wlt at pop.umn.edu
University of Minnesota
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