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From |
Steven Samuels <sjhsamuels@earthlink.net> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: svy: tabulate or proportions |

Date |
Wed, 30 Jul 2008 16:45:30 -0500 |

Ouch! I meant "the responses that Stas, Sergiy, and I wrote"! The last time I so mixed up names, I called Nick Cox, "Professor Cross", after an old colleague. Apologies to all concerned. -Steve Chao, As far as I can tell, you haven't asked a different question here. If you reread the responses that Austin and I wrote, I'm sure you will find your question answered. -Steven On Jul 29, 2008, at 4:54 PM, Chao Yawo wrote: > Thanks very much. I probably wasn't too clear in my original post > > I am examining the relationship between HIV testing behaviors (whether > people plan to take the test, etc) and a number of socio-demographic > and epidemiological variables. At a minimum, I wanted to understand > the distribution of all my predictors before running crostabs > procedures. > > I know svy: tab can produce both the estimated proportions (just like > the %s displayed in frequency tables) and the crosstab estimates. And > both of these allow one to make assumptions about the underlying > population. > > Hence the question -- whether it is appropriate to use the svy: > estimation commands once I am dealing with such a survey sample... or > to revert to non-survey commands. > > thanks - CY > > > ---------------------- > On Tue, Jul 29, 2008 at 12:36 PM, Stas Kolenikov > <skolenik@gmail.com> wrote: >> On 7/25/08, Chao Yawo <Yawo1964@yahoo.com> wrote: >>> I am using svy commands to analyze a DHS dataset. >>> >>> As a usual prerequisite, I want to run some descriptive >>> statistics on >>> my sample. I can use the regular tabulate or fre commainnd to >>> produce >>> frequency distributions. >>> >>> However, I realized that svy has a "tabulate" or "proportions" >>> option >>> that could produce frequency distributions/estimates per >>> variable. I >>> run both and realized slight differences between the two >>> frequencies >>> outputs. >>> >>> Which one should I use - I am leaning towards using the one with >>> the >>> svy: prefix. >>> >>> I would appreciate any thoughts and pointers. >> >> Well as Steven said, what is it exactly that you want to figure out? >> If you want to see whether you have cells with zero or low counts, >> then either -tab- or -svy : tab- will do. If you want to get any idea >> of the underlying population, you MUST use -svy-. >> >> Let's think through a grocery shopping example. Suppose somebody >> looked at your fridge and counted how many gallons of milk you have >> there, how many eggs, the total weight of vegetables, etc. If they >> want to figure out a diet of a given person, then that's all the data >> they need. If they wanted to figure out what's available in your >> grocery store, or what's a diet of an average person, then there is >> more work to do: they need to figure out how often you buy any >> particular food. May be you are a vegetarian, and skip the meat rows >> in your supermarket -- so your fridge will not provide any >> information >> about meat consumption, and estimates of protein intake based on your >> fridge only will be biased. The "how frequently" question is what you >> also know as sampling weights, based on inverse probabilities of >> selection. >> >> So if you want something that's specific to your sample, you can have >> a go without -svy- options. Will that be interesting to anybody? >> Probably not. Whichever summaries you want to produce out of your >> data >> will only be interesting to the extent that they describe the >> population -- and then you need to use the survey design information. >> >> -- >> Stas Kolenikov, also found at http://stas.kolenikov.name >> Small print: I use this email account for mailing lists only. >> * >> * 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/

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