Its late in the day, so maybe I'm just tired, but -svytab- appears to be
acting strangely. If you run -svytab- with no options, a table is printed
with the cell proportions, and a corresponding vector e(b) is saved. If you
run -svytab- with the -col- option it prints the column proportions, but
e(b) still contains the regular cell proportions. This may not seem
exceedingly strange since it is easy enough to derive the column proportions
from the cell proportions for display purposes. However, if, in addition to
the -col- option, you also specify the -se- option (which prints the
standard errors in the table beneath the proportion estimates), then e(b)
contains the column proportions not the cell proportions. Is it just me, or
is that a little counter-intuitive? Wouldn't it be better to always return
the column proportions in e(b) when the -col- option is specified rather
than making it dependent on also specifying the -se- option?
Also, everything that I just said about the estimate vector e(b) applies
equally to the variance matrix e(V), which is even more sinister because its
harder to spot an error in the variance than in the estimate itself.
My log file it appended below.
Thanks,
Lee
Lee Sieswerda, Epidemiologist
Thunder Bay District Health Unit
999 Balmoral Street
Thunder Bay, Ontario
Canada P7B 6E7
Tel: +1 (807) 625-5957
Fax: +1 (807) 623-2369
[email protected]
www.tbdhu.com
----------------------------------------------------------------------------
----------------
log: C:\DATA\weird.log
log type: text
opened on: 10 Jun 2002, 18:12:55
. svytab can12m tob12m
pweight: weight2 Number of obs =
2679
Strata: strata2 Number of strata =
6
PSU: schoolid2 Number of PSUs =
23
Population size =
2673.6008
-------------------------------------
used |
cannabis | smoked cigarettes past 12
past 12 | months
months | no(incl yes Total
----------+--------------------------
no | .5521 .0768 .6289
yes | .1595 .2116 .3711
|
Total | .7116 .2884 1
-------------------------------------
Key: cell proportions
Pearson:
Uncorrected chi2(1) = 611.6705
Design-based F(1, 17) = 434.4571 P = 0.0000
. mat li e(b)
e(b)[1,4]
p11 p12 p21 p22
y1 .55209713 .07676658 .1595441 .21159219
. mat li e(V)
symmetric e(V)[4,4]
p11 p12 p21 p22
p11 .00081594
p12 .0002619 .00018399
p21 -.00090858 -.00043875 .00124971
p22 -.00016925 -7.135e-06 .00009762 .00007877
. svytab can12m tob12m, col
pweight: weight2 Number of obs =
2679
Strata: strata2 Number of strata =
6
PSU: schoolid2 Number of PSUs =
23
Population size =
2673.6008
-------------------------------------
used |
cannabis | smoked cigarettes past 12
past 12 | months
months | no(incl yes Total
----------+--------------------------
no | .7758 .2662 .6289
yes | .2242 .7338 .3711
|
Total | 1 1 1
-------------------------------------
Key: column proportions
Pearson:
Uncorrected chi2(1) = 611.6705
Design-based F(1, 17) = 434.4571 P = 0.0000
. mat li e(b)
e(b)[1,4]
p11 p12 p21 p22
y1 .55209713 .07676658 .1595441 .21159219
. mat li e(V)
symmetric e(V)[4,4]
p11 p12 p21 p22
p11 .00081594
p12 .0002619 .00018399
p21 -.00090858 -.00043875 .00124971
p22 -.00016925 -7.135e-06 .00009762 .00007877
. svytab can12m tob12m, col se
pweight: weight2 Number of obs =
2679
Strata: strata2 Number of strata =
6
PSU: schoolid2 Number of PSUs =
23
Population size =
2673.6008
-------------------------------------
used |
cannabis | smoked cigarettes past 12
past 12 | months
months | no(incl yes Total
----------+--------------------------
no | .7758 .2662 .6289
| (.0468) (.0359) (.039)
|
yes | .2242 .7338 .3711
| (.0468) (.0359) (.039)
|
Total | 1 1 1
|
-------------------------------------
Key: column proportions
(standard errors of column proportions)
Pearson:
Uncorrected chi2(1) = 611.6705
Design-based F(1, 17) = 434.4571 P = 0.0000
. mat li e(b)
e(b)[1,4]
p11 p12 p21 p22
y1 .77580824 .26621899 .22419176 .73378101
. mat li e(V)
symmetric e(V)[4,4]
p11 p12 p21 p22
p11 .00219031
p12 .00157459 .00129206
p21 -.00219031 -.00157459 .00219031
p22 -.00157459 -.00129206 .00157459 .00129206
. log close
log: C:\DATA\weird.log
log type: text
closed on: 10 Jun 2002, 18:13:28
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