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From |
Steven Samuels <sjsamuels@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: weights in pooled repeated cross sections |

Date |
Wed, 28 Sep 2011 09:12:00 -0400 |

I think that the notion of an "average population" is not only useful but often unavoidable, even for single year surveys. Many of these are conducted over a period of months, sometimes, for continuous surveys, over 12 months. As such, the population represented is the "average population" for the time period. Austin Nichols once suggested that the proper denominator for multi-year surveys should be not persons, but "person-years". This is just another version of the "average population" over the for the survey period. Even more: many national yearly surveys provide modified weights so that population frequencies of important characteristics (age, gender, ethnic group) match the frequencies in recent censuses. Steve On Sep 28, 2011, at 4:36 AM, Ivica Rubil wrote: Steve, Cameron: According to the paper that Cameron suggested me to read: " It is not a lways necessary to adjust the weights when pooling the dat a . When weights are adjusted , the assumption is that they are being adjusted to properly represent a population. The problem is that when we ight s f rom di ff e r ent t ime pe r iods a r e combined, the r e sul t ing we ight s do not represent the current population, but rather, an average population that does not exist. Consequently, creating tot a l s wi th a combined f i l e may not b e a p p r o p r i a t e , wh e t h e r o r n o t t h e we ight s a r e adjus t ed. On the othe r hand, r a t ios , propor t ions and me ans can be regarded as useful statistics when cons ide r ed a s pe r iod e s t ima t e s . For these types of statistics, the results using the original weights or the weights that have be en adjus t ed us ing a common factor 1/k (k= # of datasets combined) will give the same result. This a l so holds for r e gr e s s i o n p a r a m e t e r s , whe r e we ight s a r e us ed in the mode l in order to take the survey design into account rather than to make estimates for some f ini t e popul a t ion. -- Ivica Rubil Ekonomski institut / The Institute of Economics, Zagreb Trg J. F. Kennedyja 7, 10 000 Zagreb, Croatia tel. +385-1-2362-269 fax. +385-1-2335-165 irubil@eizg.hr www.eizg.hr -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Cameron McIntosh Sent: 28. rujan 2011 0:17 To: STATA LIST Subject: RE: st: weights in pooled repeated cross sections Ivaca, Strategies for dealing with your type of situation are dealt with in: Thomas, S., & Wannell, B. (2009). Combining cycles of the Canadian Community Health Survey. Health Reports, 20(1).http://www.statcan.gc.ca/pub/82-003-x/2009001/article/10795-eng.pd f Cam ---------------------------------------- > Subject: Re: st: weights in pooled repeated cross sections > From: sjsamuels@gmail.com > Date: Tue, 27 Sep 2011 17:30:10 -0400 > To: statalist@hsphsun2.harvard.edu > > > Thanks, Nick. I missed that part of Ivica's question. > > > To Ivica, I would say: you can usually find a description of the study design and variables in the study manuals and reports. For example, the 2008 Survey is described in www.dzs.hr/Eng/Publication/2009/SI-1400.pdf and contains the statement: > > "In the year 2008, the Household Budget Survey sample was selected in two stages. In the first one there were 467 segments selected (segments are groups of neighbouring enumeration areas) out of segments previously selected for the 2008 Labour Force Survey. In the second stage, out of each of selected segments, 10 dwellings, occupied by private households, were selected, which were not previously selected into the 2008 Labour Force Survey. Thus, 4 670 dwellings occupied by private households were selected. At each selected occupied dwelling all private households were interviewed." > > This says nothing about previous years, but the answer might lie in reports about the Labor Force Survey. You should contact the Central Bureau of Statistics. If they have a web site, the reports might be there. > > A survey analysis which does not account for the design variables-strata, PSUs- will produce standard errors and p-values which are too small, usually much too small. Such an analysis assumes that the observations are independent, whereas the effective sample size is more the number of PSUs than the number of households. > > > Regards, > > Steve > > > > On Sep 27, 2011, at 4:35 PM, Nick Cox wrote: > > PSUs are primary survey units. > > Nick > > On Tue, Sep 27, 2011 at 9:32 PM, Steven Samuels <sjsamuels@gmail.com> wrote: >> >> 1. Pool >> 2. Divide weights by four (would affect only totals, but still a good idea) >> 3. -svyset- the whole thing. >> >> >> Steve >> >> On Sep 27, 2011, at 10:40 AM, Ivica Rubil wrote: >> >> so, you're saying I just pool the 4 datasets, divide the weights by 4, >> and apply -svyset- to the pooled dataset? Or should I rather use >> -svyset- for each of the 4 datasets, pool them in one, and then divide >> the weights by 4? >> Further, sorry for bothering you: what are PSUs? How do I check if they >> change form year to year? >> >> -- >> Ivica Rubil >> Ekonomski institut / The Institute of Economics, Zagreb >> Trg J. F. Kennedyja 7, 10 000 Zagreb, Croatia >> tel. +385-1-2362-269 >> fax. +385-1-2335-165 >> irubil@eizg.hr >> www.eizg.hr >> >> >> -----Original Message----- >> From: owner-statalist@hsphsun2.harvard.edu >> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steven >> Samuels >> Sent: 27. rujan 2011 15:51 >> To: statalist@hsphsun2.harvard.edu >> Subject: Re: st: weights in pooled repeated cross sections >> >> >> Ivica- >> You can use the individual weights, Ivica, but divide by 4 so that they >> sum to the average population total over the four years >> >> You still have to write the rest of the -svyset- command. If the PSUs >> did not change over the four years, then treat the pooled sample as one >> large sample, and use the same -svyset- statement that you would use for >> a single year. If some PSUs changed you will have to do some stratum >> recoding. For an example see >> http://www.cdc.gov/nchs/ppt/nchs2010/46_Moriarity.ppt >> >> Steve >> >> On Sep 26, 2011, at 12:03 PM, Ivica Rubil wrote: >> >> Dear all, >> >> I am trying to pool four repeated cross-sections of Croatian Hpusehold >> Budget Survey. >> For each year that I want to pool, I have sampling weights for each >> observation (both household and person). >> My questions are: What should I do with the weights once I pool the four >> datasets? Is it wrong to use >> dataset-specific weights in the pooled dataset and just run estimation >> commands with the weight option, if >> available? I am confused. Please, help. >> > > * > * 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/ * * 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/ * * 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/

**References**:**FW: st: weights in pooled repeated cross sections***From:*"Ivica Rubil" <irubil@eizg.hr>

**Re: st: weights in pooled repeated cross sections***From:*Steven Samuels <sjsamuels@gmail.com>

**Re: st: weights in pooled repeated cross sections***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: weights in pooled repeated cross sections***From:*Steven Samuels <sjsamuels@gmail.com>

**RE: st: weights in pooled repeated cross sections***From:*Cameron McIntosh <cnm100@hotmail.com>

**RE: st: weights in pooled repeated cross sections***From:*"Ivica Rubil" <irubil@eizg.hr>

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