[DDI-users] Variable representation

[Rémi Dewitte]

Hello,

I need try to figure how to express that a single variable can have an array
value (which can be treated as a bag if order is irrelevant) now :).
There are several advantages when using this kind of variables in the
analysis. It happens to have 40 codes in a code scheme for a question, we
would like to avoid creating/deleting/modifying variables when the code
scheme changes. And it is convenient when doing statistics/crosstabs, you
don't have to do as many crosstabs as there are of codes for example.

What about numeric representation able to reference a code scheme ?

Thanks a lot,
Rémi

On Wed, Apr 15, 2009 at 16:24, Wendy Thomas <wlt at pop.umn.edu> wrote:

> 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
>>>
>>> _______________________________________________
>>> DDI-users mailing list
>>> 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
> 50 Willey Hall
> 225 19th Avenue South
> Minneapolis, MN 55455
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