Dear Thomas,
Thanks a lot for your reply which helps a lot. *From:* Thomas Lumley-2 [via R] [mailto: [email protected]] *Sent:* 25 September 2012 22:49 *To:* Kristof *Subject:* Re: Three Stage Sampling of categorical variable using 'survey' in R On Wed, Sep 26, 2012 at 12:45 AM, Kristof <[hidden email]</user/SendEmail.jtp?type=node&node=4644179&i=0>> wrote: > 1) SURVEY DESIGN > So far I designed mainly two stage cluster surveys but never did a three > stage cluster survey design. It seems that in the analysis only the PSU is > taken into account and enumeration area. So whatever happens at the second > stage seems irrelevant to the analysis which seem odd to me. There are two issues here that aren't the same. If you don't provide population size information the analysis depends only on the PSU, strata, weights, and measurements. *[KB=>] Population is 38.8 Million (we can have an exact figure and make a fairly accurate projection based on population growth rate. Sample at this time is around 7800 so around 5% of the sample.* If the sample is much smaller than the population, then even if you do provide population size information the analysis essentially depends only on the PSU, strata, weights, and measurements. *[KB=>] I assume 5% is small and no FPC is required* This doesn't mean that the design doesn't matter after stage 1, it just means that the weights and the distribution of the measurements tells you everything about the subsequent stages that you need to know. In particular, the variability in weight*data is important, and different designs can give very different standard errors. *[KB=>] Thanks for that this is clear PSU information to determine the deff and all stages below are accounted in the sample weight* The same design principles apply at later stages of design as at stage 1: stratifying on a variable correlated with the variable of interest will increase precision, and the Neyman allocation formula still tells you how to choose stratum sizes based on what you know about variance and cost. *[KB=>] That is clear* It's harder to optimize a multistage design because there are many more options and which design is best will depend on a lot of things you don't know, but it's not intrinsically different from optimising a single-stage design. *[KB=>] *Now I see how the other staegs are taken into account in the analysis I can see that > Our intention was to do a PPM at the first and the second stage and have > same size takes in each enumeration area. > The design would be to select 50 out of 150 Upazila's (sub-districts) as > PSU using probability proportionate to size. > The second stage would be 6 village-groups out of an average of 250 > village-groups per Upazila using PPS > use SRS to select 26 households in each of the 6 selected villages per > Upazila. Total sample size 7800 > Household is the BSU and where we need to calculate information on the > individual level we are confident to be able to correct the sample weights > for that. That sounds plausible *[KB=>] *Reassuring to here and thanks for the demystification. The unknown seem sometimes more daunting than it is. Will discuss this with the team but Iâm sure they are grateful for your help. -thomas *[KB=>] *Kristof -- Thomas Lumley Professor of Biostatistics University of Auckland ______________________________________________ [hidden email] </user/SendEmail.jtp?type=node&node=4644179&i=1> mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ------------------------------ *If you reply to this email, your message will be added to the discussion below:* http://r.789695.n4.nabble.com/Three-Stage-Sampling-of-categorical-variable-using-survey-in-R-tp4644110p4644179.html To unsubscribe from Three Stage Sampling of categorical variable using 'survey' in R, click here<http://r.789695.n4.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=4644110&code=Ym9zdG9lbkBpcmMubmx8NDY0NDExMHw5Njg1MzMzOTY=> . NAML<http://r.789695.n4.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> -- <http://www.irc.nl/page/73684> -- View this message in context: http://r.789695.n4.nabble.com/Three-Stage-Sampling-of-categorical-variable-using-survey-in-R-tp4644110p4644200.html Sent from the R help mailing list archive at Nabble.com. [[alternative HTML version deleted]]
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