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From | Laurie Molina <molinalaurie@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: Controlling for atrittion in panel, or creating a panel without atrittion |
Date | Thu, 23 Feb 2012 09:35:56 -0600 |
Thank you brendan! On Thu, Feb 23, 2012 at 4:31 AM, Brendan Halpin <brendan.halpin@ul.ie> wrote: > On Thu, Feb 23 2012, Laurie Molina wrote: > >> 1. To take a random sample at the first period and then merge the >> databases to have a panel. In this case my panel will have attrition. >> In fact by the last period the attrition rate (comparing period 1 >> observations with period 10 observations will be of almost 50%). The >> remaining sample size much smaller than the original sample size is >> leading to representativeness issues. > > Yes, your sub-sample will have attrition bias, but in a way that > reflects that of your main sample. That is, if your main sample is > representative in wave 1 and then suffers from attrition, this is > probably a good option, but if subjects can meaningfully enter the main > sample after wave 1 perhaps not. > > >> 2. To take a random sample of the observations that appear on the >> database in all the periods. If attrition is not random, then i would >> have a population that is different to the original population, and >> hence my random sample may not be representative for the original >> population, but only for the population defined by all the >> observations that appear in the database in all periods. > > Depending on what analysis you do afterwards, you may end up imposing > this restriction anyway. > >> Which option do you think i should take? > > A third option would be to take a random sample of IDs, and take all > observations available for them. This will better replicate the pattern > of missingness in the main sample. > > Which option is best depends on what analysis you want to do, and on how > the main sample is collected (in particular, in what way and at what > time it is representative), > > Brendan > -- > Brendan Halpin, Department of Sociology, University of Limerick, Ireland > Tel: w +353-61-213147 f +353-61-202569 h +353-61-338562; Room F1-009 x 3147 > mailto:brendan.halpin@ul.ie ULSociology on Facebook: http://on.fb.me/fjIK9t > http://teaching.sociology.ul.ie/bhalpin/wordpress twitter:@ULSociology > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/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/statalist/faq * http://www.ats.ucla.edu/stat/stata/