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From | Mike Butterfield <mcbutterfield@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: SVY medians and Elixhauser |
Date | Sun, 14 Apr 2013 22:11:14 -0700 |
Hi Steve (thanks for the reference) and Stas- I had some trouble with epctile and wanted to get your opinion on whether this is ‘legal’ (legitimate) to do. 1. I tried to get median ages for my patients with portal vein thrombosis (pvt) for both those with& without cirrhosis, but I had some strata with single observations. 2. I identified the strata and excluded them (~6 observations), and got it to work. 3. Is ok to do? Output for non cirrhotics is below. a. This didn’t work: . epctile AGE, p(50) over(cirr) svy speclab subpop(pvt if AGE>=18 & AGE<=90) (running mean on estimation sample) Survey: Mean estimation Number of strata = 53 Number of obs = 3665 Number of PSUs = 482 Population size = 18356 Subpop. no. obs = 3665 Subpop. size = 18356 Design df = 429 0: cirr = 0 1: cirr = 1 -------------------------------------------------------------- | Linearized Over | Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------ __000006 | 0 | -.0236348 . . . 1 | -.0477322 . . . -------------------------------------------------------------- Note: missing standard errors because of stratum with single sampling unit. estimates post: matrix has missing values r(504); b. this did: svydes AGE if AGE>=18 & AGE<90 & pvt==1 & cirr==0 Survey: Describing stage 1 sampling units pweight: DISCWT VCE: linearized Single unit: missing Strata 1: NIS_STRATUM SU 1: HOSPID FPC 1: <zero> #Obs with #Obs with #Obs per included Unit #Units #Units complete missing ---------------------------- Stratum included omitted data data min mean max -------- -------- -------- -------- -------- -------- -------- -------- 2111 1* 0 1 0 1 1.0 1 2412 1* 0 1 0 1 1.0 1 3111 1* 0 1 0 1 1.0 1 3112 1* 0 1 0 1 1.0 1 3121 1* 0 1 0 1 1.0 1 4112 1* 0 1 0 1 1.0 1 4122 1* 0 4 0 4 4.0 4 -------- -------- -------- -------- -------- -------- -------- -------- 51 399 0 1495 0 1 3.7 69 ------------------ . epctile AGE, p(50) svy speclab subpop(pvt if AGE>=18 & AGE<=90 & cirr==0 & NIS_STRATUM ~=2111 & NIS_STRATUM ~=2412 & NIS_STRATUM ~=3111 & NIS_STRATUM ~=3112 & NIS_STRATUM ~=3121 & NIS_STRATUM ~=4112) Number of strata = 44 Number of obs = 1492 Number of PSUs = 394 Population size = 7486.8 Subpop. no. obs = 1492 Subpop. size = 7486.8 Design df = 350 ... Percentile estimation ------------------------------------------------------------------------------ | Linearized AGE | Coef. Std. Err. z P>|z| [95% Conf. Interval] -------------+---------------------------------------------------------------- p50 | 56 .75 74.67 0.000 54.53003 57.46997 Mike * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/