Re: st: Problems with expand og reverting to original dataset

[Ada Ma <heu034@googlemail.com>]

Apologies...  I meant:

"With more than two siblings "

I meant to write more.. here it is - the best strategy IMHO is to
include all samples you have, otherwise how can you say that your
research results is representative of the population.  If you are
drawing 2 random people per family then you have to pay a lot of care
- so that e.g. it does NOT mean that people from families with larger
number of siblings are less likely to be chosen, or that people from
large families are less likely to be exhibiting some selection
criteria you are applying (e.g. fewer than five years apart).

HTH,

Ada



On Thu, Jan 20, 2011 at 5:01 PM, Ada Ma <heu034@googlemail.com> wrote:
> Hi Grethe
>
> WRT your Q to Nick the command you should write is:
>
> bysort mother_id father_id (birth_date) : gen diff = birth_date[_n+1]
> -birth_date
>
> With more than one sibling I guess you need to choose the one who have
> the most "within 5 years" as the index sibling.
>
> What regression are you trying to run?  Others might have better
> suggestions how to set up your data set depending on what regressions
> you are going to run.
>
> Regards,
> Ada
>
>
>
> On Thu, Jan 20, 2011 at 2:12 PM, Grethe Søndergaard
> <dkstatstata@gmail.com> wrote:
>> Thank you for your answers
>>
>> @ Nick Cox: I have tried to run bysort mother_id father_id
>> (birth_date) : gen diff = birth_date[2] -birth_date[1]. However, an
>> error message appear: "factor variables and time-series operators not
>> allowed". Can I solve this problem - by somehow changing the type of
>> variable that birth_date is?
>>
>> @ Ada Ma: My dataset consists of more than two siblings per family
>> (one line for each person). I am not sure how to find out which
>> siblings to be included in the dataset, if more than two siblings are
>> being compared. E.g. a family consists of children age 1, 4, and 8 (so
>> who should stay in the dataset). So that is why I choose only to
>> include persons with one siblings.
>>
>>
>>
>> 2011/1/20 Nick Cox <njcoxstata@gmail.com>:
>>> Nick
>>>
>>> On Thu, Jan 20, 2011 at 1:28 PM, Ada Ma <heu034@googlemail.com> wrote:
>>>> How does your original dataset looks like?
>>>>
>>>> One line of data per person or one line of data per pair of siblings?
>>>> Do you always have 2 siblings or do you have more than 2 siblings?
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>
>
>
> --
> Ada Ma
> Research Fellow
> Health Economics Research Unit
> University of Aberdeen, UK.
> http://www.abdn.ac.uk/heru/
> Tel: +44 (0) 1224 555189
> Fax: +44 (0) 1224 550926
>



-- 
Ada Ma
Research Fellow
Health Economics Research Unit
University of Aberdeen, UK.
http://www.abdn.ac.uk/heru/
Tel: +44 (0) 1224 555189
Fax: +44 (0) 1224 550926

*
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