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From | Rebecca Pietrelli <rebecca.pietrelli@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: svyset |
Date | Fri, 2 Nov 2012 13:36:45 +0100 |
Thank you very much Stas Kolenikov! So, if the systematc procedure had worked with replacement, I could simply use: svyset psu_var [pw=hhweights_var], strata(strata1_var) I don't need to create strata2. I was wondering if I have to use the fpc. I know that it is necesary to use it with systematic procedure. Now I am confused because the first stage is a combined procedure (PPS + systematic) and the second stage is a systematic procedure. thank you Rebecca 2012/11/2 Stas Kolenikov <skolenik@gmail.com>: > This design took a lot of compromises. Systematic sampling is THE > worst sampling procedure, and the only excuse for using it is that you > only had access to paper, and could only do a long addition on the > margin of the printout of your list of EAs with cumulative population > sizes. Still, systematic sampling could hit some large units (larger > than {the total population size}/{# of units sampled}) more than once, > so it could have worked effectively with replacement (which is what > you want, without replacement is tedious to work with). > > The finite population correction is only relevant for SRS. It does not > generalize well to PPS type designs, where, technically speaking, you > should use double probabilities of selection (and if you find yourself > doing that, you would recall that the systematic sampling does not > allow unbiased variance estimation... that's why I said it is the > worst method). > > You are correct regarding strata2: you'd have to create an indicator > for the type of the HH. > > -- > -- Stas Kolenikov, PhD, PStat (SSC) :: http://stas.kolenikov.name > -- Senior Survey Statistician, Abt SRBI :: work email kolenikovs at > srbi dot com > -- Opinions stated in this email are mine only, and do not reflect the > position of my employer > > On Fri, Nov 2, 2012 at 6:06 AM, Rebecca Pietrelli > <rebecca.pietrelli@gmail.com> wrote: >> Hi, >> >> I really hope anyone can help me. >> I am using the Stata command svyset in order to declare the survey >> design to files of my dataset (Uganda Migration Housolds Survey 2010). >> >> The sampling design is two-stage stratified. >> In the first stage: enumeration areas - EAs - (PSU) were selected, >> separately for rural and >> urban areas. The applied procedure is a PPS (proportionally done based >> on the number of households in the respective stratum according to the >> 2006 Uganda household survey) combined with a systematic approach. >> In the second stage: households were selected in each EA, using a >> systematic procedure (4 hhs with international migrants, 3 with >> internal migrants and 3 without migrants). >> >> I think to use the following command: >> >> svyset psu_var [pw=hhweights_var], strata(strata1_var) fpc(fpc1) || >> _n, strata(strata2_var) fpc(fpc2). >> >> I have the following doubts: >> >> 1) I am not sure if the first stage is with or without replacement (It >> is not mentioned in any part of the report!!!). I suppose that a PPS >> combined with a systematic procedure is without replacement. Is this >> assumption correct? >> >> 2) I have the strata1_var (rural or urban) but I don't have the >> strata2_var. In that case, should I create it? (for ex. strata2 = 1 if >> hh does not have migrants, = 2 if it has internal migrants and = 3 if >> it has international migrants). >> >> 3) I don't have fpc in the data. I think to create them as >> [(N-n)/(N-1)]^(1/2). So in the first stage, is N the total number of >> EAs in Uganda or is it the total number of hhs living in Uganda? >> >> Thank you very much for your help and time. >> Rebecca >> >> >> >> >> Thank you very much for any help. >> Rebecca >> * >> * 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/ > * > * 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/