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Re: st: Using stratified samples in STATA / giving weights |

Date |
Tue, 8 Sep 2009 17:47:02 -0400 |

-- Thomas, I want to more directly answer part of your question. I believe you have two strata. The basic sample weight for observations in a stratum is : N/n where N is number of population elements in the stratum, and n = the number in the sample. However if you know other information about the population other than that used to form the strata , you can use it to improve the weights. See sections on post-stratification in the books I referenced. Steve On Tue, Sep 8, 2009 at 12:29 PM, <[email protected]> wrote: > Thomas Your knowledge about weights is faulty--weights are usually >>1, for an observation's weight is the number of population members > represented by the observation (the weight can be non-integer). > Weights <1 do arise, but not in the sample that you are describing. > Before going any further. I suggest that you read Sharon Lohr. > Sampling: Design and Analysis, Duxbury, 1999). Also, look at her > section on sample size calculations. The particular sample size > calculation will depend on the purpose of your survey--whether > descriptive or analytic. If the latter than do not use the finite > population correction. If you know a lot of about your population, > you can also apply post-stratification techniques. > > The book "Sampling of Populations" by Levy and Lemeshow (Wiley) has > some Stata examples, although they are limited to descriptive samples. > > Regards, > > -Steve > > > On Sat, Sep 5, 2009 at 11:26 AM, Thomas Klausch<[email protected]> wrote: >> Dear list members, >> >> I am planning to survey a stratified sample from a relatively small finite >> population of which I know the size. I am not too familiar with weighting >> techniques and the STATA -svy- command family, which is why I write. Maybe >> somebody can give useful advice. >> >> My popluation consists of size n=8800, with n=900 and n=7900 sized relevant >> stratas. I decided to sample n=600 from each of the STRATAs since I am >> particularly interested in estimates from the smaller strata. >> >> My knowledge about weighting tells me that this gives rise to weights of >> approx. .20 for the small strata and approx. 1.80 for the large strata. In >> SPSS I would know how to use the weights function, as there is only one. >> STATA provides several weight options -fweight-, -pweight-, -aweight- and >> -iweight-. I have tested in STATA that it gives the same estimates using >> -iweight- than SPSS does using the WEIGHT BY command. >> >> My first question is if -iweight- is reasonable to use for my case when >> estimating regression models (in particular logistic panel models). >> My second question is whether there is a, maybe better, way to use the >> options provided in the -svy- command family to specify the survey design. >> maybe there is also a third way I do not know of. >> >> If anybody could give advice or further reference for detailed information >> on -svy- I'd appreciate it a lot. >> >> Many thanks >> >> Thomas >> >> * >> * 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/ >> > > > > -- > Steven Samuels > [email protected] > 18 Cantine's Island > Saugerties NY 12477 > USA > 845-246-0774 > -- Steven Samuels [email protected] 18 Cantine's Island Saugerties NY 12477 USA 845-246-0774 * * 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/

**Follow-Ups**:**Re: st: Using stratified samples in STATA / giving weights***From:*Thomas Klausch <[email protected]>

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