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From |
Steven Samuels <sjsamuels@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Confidence intervals for survey data from the estimation matrices |

Date |
Wed, 20 Jul 2011 00:19:17 -0400 |

-svy: tab- calculates SEs and confidence intervals on logit transforms of the proportions, then transforms the interval-endpoints back as "lb" and "ub". This guarantees lb>0 and ub<1. You can see the formula relating the SE of the proportion and the SE of the logit transform. on page 127 of the Stata 11 Survey manual. Apparently e(V) contains the SE of the proportion. Steve sjsamuels@gmail.com On Jul 19, 2011, at 10:55 PM, Darren White wrote: Hello, I am attempting to compile estimate tables directly from STATA's temporary estimate matrices, however none of the listed matrices after command: ereturn list (below) contain the confidence intervals that are displayed using the svy: command in STATA (table below). Also the estimate variance matrix e(V) and the square root e(V) x 1.96 +/- give the estimates in the automatic estimate display ( below at bottom) after some renaming of the e(b) and e(V) matrices but these are different to those returned form the svy: tab command. Can anyone tell me how STATA arrives at the confidence interval estimates using the svy: tab command and where they could be found in the matrix environment? Alternatively how would I replicate the calculation routine for survey data using the variance provided in the e(V) matrix? The e(b) matrix has the same percentage estimates as returned form the svy: tab agecat bmicat, ci command Any help or suggestions would be greatly appreciated Darren White Population Epidemiology Unit Queensland Health Brisbane Australia ___________________________________________________________________ . svy: tab agecat bmicat, ci per (running tabulate on estimation sample) Number of strata = 1 Number of obs = 7 Number of PSUs = 7 Population size = 7 Design df = 6 ------------------------------------------------- bmicat | percentages lb ub ----------+-------------------------------------- 1 | 42.86 9.06 84.95 2 | 57.14 15.05 90.94 | Total | 100 ------------------------------------------------- _____________________________________________________________________ . ereturn list scalars: e(stages) = 1 e(census) = 0 e(singleton) = 0 e(N_strata_omit) = 0 e(df_r) = 6 e(N) = 7 e(N_strata) = 1 e(N_psu) = 7 e(N_pop) = 7 e(r) = 1 e(c) = 2 e(total) = 7 e(mgdeff) = . e(cvgdeff) = . e(rank) = 1 macros: e(cmdline) : "svy : tab agecat bmicat, ci per" e(cmd) : "tabulate" e(prefix) : "svy" e(cmdname) : "tabulate" e(marginsnotok) : "_ALL" e(predict) : "_no_predict" e(estat_cmd) : "svy_estat" e(colvar) : "bmicat" e(rowvar) : "agecat" e(setype) : "cell" e(vcetype) : "Linearized" e(vce) : "linearized" e(wtype) : "pweight" e(wvar) : "weight" e(wexp) : "= weight" e(singleunit) : "missing" e(depvar) : "Mean" e(properties) : "b V" matrices: e(b) : 1 x 2 e(V) : 2 x 2 e(V_srs_col) : 2 x 2 e(Deft_col) : 1 x 2 e(Deff_col) : 1 x 2 e(V_srs_row) : 1 x 1 e(Deft_row) : 1 x 1 e(Deff_row) : 1 x 1 e(V_srs) : 2 x 2 e(Deft) : 1 x 2 e(Deff) : 1 x 2 e(V_col) : 2 x 2 e(V_row) : 1 x 1 e(Col) : 1 x 2 e(Row) : 1 x 1 e(Prop) : 1 x 2 e(Obs) : 1 x 2 e(_N_strata_certain) : 1 x 1 e(_N_strata_single) : 1 x 1 e(_N_strata) : 1 x 1 _________________________________________________________________________________________ . ereturn post b V . ereturn display Coef. Std. Err. z P>z [95% Conf. Interval] p11 .4285714 .2020305 2.12 0.034 .0325989 .8245439 p12 .5714286 .2020305 2.83 0.005 .1754561 .9674011 ________________________________________________________________________________________ ******************************************************************************** This email, including any attachments sent with it, is confidential and for the sole use of the intended recipient(s). This confidentiality is not waived or lost, if you receive it and you are not the intended recipient(s), or if it is transmitted/received in error. Any unauthorised use, alteration, disclosure, distribution or review of this email is strictly prohibited. The information contained in this email, including any attachment sent with it, may be subject to a statutory duty of confidentiality if it relates to health service matters. 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**References**:**st: Confidence intervals for survey data from the estimation matrices***From:*"Darren White" <darrenm.white@health.qld.gov.au>

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