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st: Confidence intervals for survey data from the estimation matrices
From
"Darren White" <[email protected]>
To
<[email protected]>
Subject
st: Confidence intervals for survey data from the estimation matrices
Date
Wed, 20 Jul 2011 12:55:18 +1000
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
________________________________________________________________________________________
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