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st: Using istdize


From   "Banham, David (DHS)" <David.Banham@dhs.sa.gov.au>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   st: Using istdize
Date   Mon, 9 Feb 2004 16:01:55 +1030

I wondered if someone could offer some advice to a relative new user at
using Stata for indirect standardisation please?

I have a standard population dataset ("C:\Stata8\standard_pop.dta") that
contains the variables:
sex(2 levels) & age(9), pop_pop (population for sex-age level) and pop_dv
(outcome variable for sex-age level).
The working file also contains variables of quint(5 levels of disadvantage)
& sex(2) & age(9), sty_pop (population for each qunitile, sex & age) and
sty_dv (outcome variable for quintile, sex & age level).
I wish to compare the outcome variable across disadvantage quintiles after
adjusting for sex and age and used.... 

istdize sty_dv sty_pop sex age using "C:\Stata8\standard_pop.dta", by(quint)
pop(pop_dv pop_pop) print

The resultant output makes sense to me in that:
For the Standard Population it lists the relevant stratum specific rates by
sex and age;
For the Indirect Standardization output it shows appropriate figures in each
Quintile for the Standard Population Rate, the Observed Population and Cases
Expected.

What doesn't make sense to me is the Observed Case numbers.  The total for
Observed cases at the end of output for each Quintile is different to the
total appearing in the Summary.  Neither of the figures correspond to the
actual Quntile total  either.

I've appended part of the relevant output below.....   

-----------Standard Population-----------
           Stratum               Rate
----------------------------------------
        1        1              0.03645
        1        2              0.00445
        1        3              0.02461
        1        4              0.03507
        1        5              0.04074
        1        6              0.06241
        1        7              0.12544
        1        8              0.25994
        1        9              0.46857
        2        1              0.02632
        2        2              0.00333
        2        3              0.00871
        2        4              0.01352
        2        5              0.02323
        2        6              0.04227
        2        7              0.08375
        2        8              0.16200
        2        9              0.36878
----------------------------------------
Standard population's crude rate:       0.07397

-------------------------------------------------------------------
-> quint= 1 
                            Indirect Standardization   
 
                            Standard                     
                           Population     Observed      Cases    
           Stratum            Rate       Population    Expected 
-------------------------------------------------------------------
     Male      0-4           0.0365    1115452544  40660135.98
     Male     5-14           0.0044    2265765376  10072570.72
     Male    15-24           0.0246    2039920384  50198037.35
     Male    25-34           0.0351    2297000448  80553976.10
     Male    35-44           0.0407    2285767936  93119707.91
     Male    45-54           0.0624    1862058624 116201829.23
     Male    55-64           0.1254    1328392704 166632918.91
     Male    65-74           0.2599    1057590272 274912490.84
     Male      75+           0.4686     694986944 325651230.22
   Female      0-4           0.0263    1062510656  27963572.39
   Female     5-14           0.0033    2159252224   7186185.90
   Female    15-24           0.0087    1934393216  16845861.98
   Female    25-34           0.0135    2232171264  30178037.63
   Female    35-44           0.0232    2228566016  51775768.18
   Female    45-54           0.0423    1887901056  79809596.97
   Female    55-64           0.0838    1323544832 110852900.03
   Female    65-74           0.1620    1130700800 183175459.27
   Female      75+           0.3688    1057105536 389840996.20
-------------------------------------------------------------------
Totals:                               299630808322055631275.83

                                                 Observed Cases:218401328
                                                  SMR (Obs/Exp):     0.11
                            SMR exact 95% Conf. Interval: [0.1062, 0.1063]
                                                     Crude Rate:   0.0073
                                                  Adjusted Rate:   0.0079
                                      95% Conf. Interval: [0.0079, 0.0079]

Summary of Study Populations (Rates):

                Cases
    quint    Observed     Crude   Adj_Rate  Confidence Interval
--------------------------------------------------------------------------
        1  102949656  0.007289   0.007859  [0.007858, 0.007860]
        2   49972660  0.006685   0.006631  [0.006630, 0.006632]
        3   96338672  0.002175   0.001966  [0.001966, 0.001967]
        4   77413256  0.000559   0.000603  [0.000602, 0.000603]
        5   29363224  0.003253   0.003167  [0.003166, 0.003168]
 
 
Summary of Study Populations (SMR):

                Cases        Cases                   Exact
    quint    Observed     Expected    SMR     Confidence Interval
--------------------------------------------------------------------------
        1  102949656     2.06e+09   0.106    [0.106231, 0.106259]
        2   49972660     2.21e+09   0.090    [0.089636, 0.089661]
        3   96338672     2.49e+09   0.027    [0.026575, 0.026587]
        4   77413256     2.02e+09   0.008    [0.008145, 0.008152]
        5   29363224     2.36e+09   0.043    [0.042807, 0.042823]
 
Any help on this is much appreciated.

Yours quizzically, 

David Banham 
Epidemiologist 
Strategic Planning & Research Branch 
Department of Human Services 
PO Box 6 Rundle Mall 
Adelaide SA 5000 
Phone:  61 8  8226 0786 
Fax:  61 6  8826 6700 
E-mail: David.Banham@dhs.sa.gov.au 
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