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st: Re: Bootstrap


From   "victor michael zammit" <vmz@vol.net.mt>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: Bootstrap
Date   Mon, 10 Apr 2006 14:42:08 +0200

Hello Statalisters,
I am trying to find out if the number of repetitions in the process of
bootstraping ,has any weight on the reliability of the  process  .In so
doing I have  run the following program  for 1000 reps and for 100 reps ,for
which I got the output ,pasted after the program .

qui

clear
set obs 100
gen a = int(invnorm(uniform()))*25+75
gen aa = _n
sort aa
save a,replace

local i = 1
while `i'<= 100  {
use a,clear
sample 1
drop aa
rename a b
gen aa = `i'
sort aa
save b`i',replace
local i = `i'+1
}
use b1,clear
local i = 2
while `i'<=100   {
merge aa using  b`i'
drop _merge
sort aa
local i = `i'+1
}
sort aa
save b,replace
merge aa using a.dta
drop _merge
order a b aa
}
tab a
tab b

........Output for 1000 reps...........
. qui


. tab a

a       Freq. Percent Cum.

25           1 1.00 1.00
50          11 11.00 12.00
75          66 66.00 78.00
100          21 21.00 99.00
125           1 1.00 100.00

Total         100 100.00

. tab b

b       Freq. Percent Cum.

25           8 0.80 0.80
50         102 10.20 11.00
75         655 65.50 76.50
100         226 22.60 99.10
125           9 0.90 100.00

Total        1000 100.00

........output for 100 reps ...........

 qui


. tab a

a Freq. Percent Cum.

25 4 4.00 4.00
50 12 12.00 16.00
75 67 67.00 83.00
100 14 14.00 97.00
125 3 3.00 100.00

Total 100 100.00

. tab b

b Freq. Percent Cum.

25 5 5.00 5.00
50 11 11.00 16.00
75 68 68.00 84.00
100 15 15.00 99.00
125 1 1.00 100.00

Total 100 100.00

...........................

I would like to be able to run this experiment for a number of times ,but
each time I would like to save the Percent of each observation in  "a "
(the  population I am interested in) and the Percent of  each  observation
in "b"  ,so that I could then test for  tendency in discrepancy ,for
different reps , given  different population sizes.
I could do it by hand ,but I suspect that it could be done more smartly .
Thanks before hand,
Victor Michael Zammit


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