Oops, on closer consideration, I remembered that the
swor and by problem was in the 2nd stage of my two
2-stage sampling routine, so I can leave the first
swor statement (with no by) as is.
For the second stage, I can replace
swor 10, by(cluster)
with
by cluster: sample 10, count
Thanks for the help! I'd still be interested to know
how one might handle the general problem of random
sampling with varying probabilities of selection.
Isn't this a common issue for survey design?
Gabriel
--- n j cox <[email protected]> wrote:
> -swor- was published in STB-59.
> I would have sworn that you don't
> now need it for your purpose,
> as -sample- has since been modified
> to support a -count- option.
>
> However, I cannot reproduce your problem.
> I can get -swor- to select the same sample
> again and again.
>
> . forval i = 1/10 {
> 2. qui sysuse auto, clear
> 3. set seed 28031952
> 4. qui swor 1, gen(select) by(foreign)
> 5. levels make, clean
> 6. }
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>
> Nick
> [email protected]
>
> Gabriel Demombynes wrote
>
> I'm using the user-written command swor to draw
> random
> samples with
> replacement. I've discovered that even when I've set
> the seed, the
> command does not always draw the same samples in
> repeated runs when
> using by. It does not have this problem when not
> using
> by.
>
> When I do the following, I get different results
> each
> time I run the
> program:
>
> set seed 6662
> use alldata, clear
> swor 1, gen(select) by(sex)
> li
>
> The problem seems to be particular to the variables
> in
> my dataset.
> When I create a new group variable, e.g. assigning
> group=1 for the
> first half of the observations, and group=2 for the
> second half, and
> then run the analysis by(group) there's no problem;
> I
> can reproduce the same results on multiple draws.
> But the problem
> persists even when I create a new group variable
> based
> on a pre-
> existing variable and use that, e.g.
>
> set seed 6662
> use alldata, clear
> gen group=1 if sex==1
> replace group=2 if sex==2
> swor 1, gen(select) by(group)
> li
>
> I've looked at the swor ado file, but I can't figure
> out what might be wrong. Any suggestions?
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