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From |
Stas Kolenikov <skolenik@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: logistic regression complex samples |

Date |
Wed, 7 Dec 2011 20:42:42 -0600 |

-svydes- command can give you an easy indication if a singleton PSU (the only PSU in a stratum) is an issue. It may also be that a wicked combination of regressors (e.g., one of the levels is only present once in the data) produces this sort of a problem: for whatever reason, the variance-covariance matrix of the estimates came out to be degenerate, and -svy- produced a default diagnostics of the singleton PSU. On Wed, Dec 7, 2011 at 7:01 PM, Antonio silva <asilva@inbox.com> wrote: > Thanks for the replies. I can run a model using SAS surveylogistic without the cluster variable but I have had difficulties to do the same with Stata version 11. I am a beginner in Stata programming.My final goal is to calculate the Archer and Lemeshow (A-L; 2006) goodness of fit test (with estat gof command) that is not available in SAS. To do that I have to run correctly the logistic regression model (with only weight and strata without cluster) in Stata. I hope someone can help with the Stata code. > Consider the following code (ex. with 2 categorical covariates) that have been used and the output . > > svyset [pweight= var_weight], strata(var_strata) > > > . xi: svy: logistic outcome i.covar1 i.covar2_3cat > > > i.covar1 _Icovar1_1-2 (naturally coded; _Icovar1_1 omitted) > i.covar2_3cat _Icovar2_3_1-3 (naturally coded; _Icovar2_3_1 omitted) > (running logistic on estimation sample) > > Survey: Logistic regression > > Number of strata = 9 Number of obs = 398 > Number of PSUs = 398 Population size = 4361.1088 > Design df = 389 > F( 0, 389) = . > Prob > F = . > > ------------------------------------------------------------------------------ > | Linearized > outcome | Odds Ratio Std. Err. t P>|t| [95% Conf. Interval] > -------------+---------------------------------------------------------------- > _Icovar1_2 | 1.926984 . . . . . > _Icovar2_~2 | .2875105 . . . . . > _Icovar2_~3 | .1978389 . . . . . > ------------------------------------------------------------------------------ > Note: missing standard errors because of stratum with single sampling unit. > > Thanks, > Antonio. >> -----Original Message----- >> From: skolenik@gmail.com >> Sent: Wed, 7 Dec 2011 11:18:37 -0600 >> To: statalist@hsphsun2.harvard.edu >> Subject: Re: st: logistic regression complex samples >> >> Antonio, >> >> it would help if you mentioned the version of Stata that you are >> using. By default, Stata would use observations as PSUs (and the >> output of -svyset- would state that -- again, it would help if you >> included the output of both commands). You can also achieve the effect >> of specifying observations as PSUs via -svyset _n ...-. >> >> On Wed, Dec 7, 2011 at 10:05 AM, Antonio silva <asilva@inbox.com> wrote: >>> Hello, >>> I would like to perform binary logistic regression in stratified >>> sampling incorporating 2 variables that represents that design >>> var_weight and var_strata. >>> Considering a model with 2 covariates , in SAS I would consider a code >>> like this that works perfectly: >>> >>> PROC SURVEYLOGISTIC DATA = dataset >>> STRATA var_strata; >>> >>> WEIGHT var_weight; >>> >>> >>> CLASS covariate1 >>> Covariate2 ; >>> >>> MODEL outcome(event='1')= covariate1 covariate2 /clparm vadjust=none ; >>> Run; >>> >>> >>> I tried an equivalent Stata code but does not work. It seems that in >>> Stata its is always necessary have the cluster variable. But in my >>> design I do not have cluster variable,only weight and strata. >>> >>> svyset [pweight= var_weight], strata(var_strata) >>> >>> svy: logistic outcome i.covariate1 i.covariate2 >>> >>> After run , in the output appears only the OR calculated and a note: >>> Note: missing standard errors because of stratum with single sampling >>> unit. >>> What is wrong with it? >>> >>> After that I did some tests considering a fictitious cluster variable >>> and worked. I suppose this command works only when the 3 design >>> variables weight strata and cluster are used at the same time. >> >> -- >> 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/ > > ____________________________________________________________ > Share photos & screenshots in seconds... > TRY FREE IM TOOLPACK at http://www.imtoolpack.com/default.aspx?rc=if1 > Works in all emails, instant messengers, blogs, forums and social networks. > > > > * > * 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/ -- 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/

**References**:**Re: st: logistic regression complex samples***From:*Stas Kolenikov <skolenik@gmail.com>

**Re: st: logistic regression complex samples***From:*Antonio silva <asilva@inbox.com>

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