[DDI-users] Variable representation
Rémi Dewitte
remi at gide.net
Thu Apr 16 04:30:02 EDT 2009
Hello,
Here is an example without the question. I have left data collection out of
the scope of my experiments for now, even I have read the schema.
The use case is a variable having the body weight of a respondent. There are
two codes (-1 and -2) indicating that the reason of a missing data. And
there is a topcode value (200). I would like to give labels for -1 -2 and
200. If you have time to have a glance at my test file and point what I may
not have understood well, it would surely help.
As for the multi choice question. I will take a variable which tells what
are all the spoken languages (among a choice of 40) in the household. More
than one is allowed. If I want to know the frequencies, I have to do 40 of
them. For each of the 40 frequency results, non-response are redundant.
Beyond simple frequencies, if the analysis software supports it, I can do
cross tabulation with "language spoken at home" and another variable more
easily than specifying 40 variables.
Thanks a lot,
Rémi
On Thu, Apr 16, 2009 at 00:09, Wendy Thomas <wlt at pop.umn.edu> wrote:
> Numeric respresenation and codeschemes are two different things. Code
> schemes can have numeric values but can be treated as either numbers or
> strings. Changes in CodeSchemes over time is done be versioning incoporating
> the old scheme and adding, subtractng, or changing content. Can you provide
> a concrete example of a question, variable, storage bundle, and analysis of
> the contents and I'll see what can be currently handled and what can't. I am
> pretty clear, I think, regarding the first 3 but not on how you are
> analyzing an unordered array other than simple frequencies.
>
> Wendy
>
>
>
> On Wed, 15 Apr 2009, Rémi Dewitte wrote:
>
> 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
>>> _______________________________________________
>>> 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
>
> _______________________________________________
> DDI-users mailing list
> DDI-users at icpsr.umich.edu
> http://www.icpsr.umich.edu/mailman/listinfo/ddi-users
>
>
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