# st: svyratio to svylogit

 From Ricardo Ovaldia <[email protected]> To [email protected] Subject st: svyratio to svylogit Date Wed, 7 Apr 2004 11:12:47 -0700 (PDT)

```Dear all,

A colleague has a survey data set of hospital
discharges and is using Stata's -svy- commands for
analysis. He first �svyset-s the data and then he uses
�svyratio- and �lincom- to compare discharge rates for
two different years. The question is how can he set
this up as a �svylogit- model? I am not very familiar
with the �svy- commands but I told him that I would
ask the list. Here is his code and results:

. svyset [pweight=cwt], strata(stratum) psu(psu)
fpc(fpc)
pweight is cwt
strata is stratum
psu is psu
fpc is fpc

. svyratio case/inhosp, by (year)

Survey ratio estimation

pweight:  cwt
Number of obs    =    310076
Strata:   stratum
Number of strata =        52
PSU:      psu
Number of PSUs   =      2468
FPC:      fpc
Population size  = 1409426.4

------------------------------------------------------------------------------
Ratio     Subpop. |   Estimate    Std. Err.   [95%
Conf. Interval]        Deff
------------------+-----------------------------------------------------------
case/inhosp       |
year==1997 |   .0003062    .0000268    .0002536
.0003589    .4295543
year==2000 |   .0003311    .0000325    .0002673
.0003949    .6767698
------------------------------------------------------------------------------
Finite population correction (FPC) assumes simple
random sampling without
replacement of PSUs within each stratum with no
subsampling within PSUs.
Weights must represent population totals for deff to
be correct when
using an FPC.  Note: deft is invariant to the scale of
weights.

. lincom [1]1 - [1]2

( 1)  [1]1997 - [1]2000 = 0

------------------------------------------------------------------------------
Ratio |   Estimate   Std. Err.      t    P>|t|
[95% Conf. Interval]
-------------+----------------------------------------------------------------
(1) |  -.0000249   .0000422    -0.59   0.555
-.0001076    .0000578
------------------------------------------------------------------------------

Ricardo.

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```