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Re: st: filling in the gaps
From
John Singhammer <[email protected]>
To
[email protected]
Subject
Re: st: filling in the gaps
Date
Mon, 21 Jan 2013 12:49:46 +0100
Martin, Jan and Nick, thank you for your help
John
On Fri, Jan 18, 2013 at 11:15 AM, Nick Cox <[email protected]> wrote:
> Maarten and Jan gave various good advice, but there is a more
> optimistic take. Use linear interpolation (strictly extrapolation) on
> -year- and -grade-. Presumably the usual pattern is to advance a grade
> each year. If that is inconsistent with the rest of the evidence the
> result will be grades with fractional parts.
>
> The command is -ipolate-
>
> Some kind of sensitivity analysis is probably still a good idea,
> notably to compare model results for the dataset with interpolation
> with those for the conservative dataset, with only definitely known
> grades and years.
>
> All that said
>
> Nick
>
> On Fri, Jan 18, 2013 at 9:14 AM, Maarten Buis <[email protected]> wrote:
>> --- Am 18.01.2013 09:21, schrieb John Singhammer:
>>>> I'm working on a dataset consisting of information on 45.000 school
>>>> children Data has been collected annually since 2009, though not
>>>> for all children Information on grade has been imported from a
>>>> national register. However, that information is only available up to
>>>> the year 2011
>>
>> --- On Fri, Jan 18, 2013 at 9:44 AM, Jan Ditzen wrote:
>>> if I understood your problem correctly the following should help:
>>>
>>> by id (sch_year), sort: replace grade = grade[_n-1]+1 if grade == .
>>
>> Technically that is true, but statistically that is typically bad
>> practice. This way you impose a very severe pattern on the grade
>> profiles of those kids. If that is what you want to study, than any
>> subsequent analysis is no longer empirical research but just
>> reproducing your assumptions.
>>
>> In general I would say that if you only have data on a key variable
>> till 2011, than that is it: you have data till 2011 and no more. If
>> you really really need those subsequent years and you really really
>> cannot wait till those data become available than you could try
>> multiple imputation (type in Stata -help mi-). However, given the fact
>> that these are complete years that are missing I would strongly
>> recommend against that. Instead I would just stick to the years
>> 2009-2011 and in a couple of years, when the data for 2012 and 2013
>> become available, write a new article for the period 2009-2013.
>>
>> -- Maarten
>>
>> ---------------------------------
>> Maarten L. Buis
>> WZB
>> Reichpietschufer 50
>> 10785 Berlin
>> Germany
>>
>> http://www.maartenbuis.nl
>> ---------------------------------
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