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| From | John Singhammer <singhammer@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| 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 <njcoxstata@gmail.com> 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 <maartenlbuis@gmail.com> 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 >> --------------------------------- >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ -- Mobile phone: +45 25 30 5867 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/