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st: R: permute test statistic


From   "Carlo Lazzaro" <carlo.lazzaro@tiscalinet.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: R: permute test statistic
Date   Thu, 30 Apr 2009 09:49:25 +0200

Dear Hugh,
are you looking for something like this (please, see example below):

............................ begin example........................
. input Mod

          Mod
  1. 1.113924
  2. 1.122969
  3. 1.057594
  4. 1.057594
  5. 1.148739
  6. .9890202
 7. .7163003
  8. .7857646
  9. .7346777
  10. .8520272
  11. .8732744
  12. .7147149
  13. end

. g Index="Mod 1" in 1/6
(6 missing values generated)

. replace Index="Mod 2" in 7/12
(6 real changes made)

. ttest Mod, by(Index) unequal

. permute Mod (r(mu_1)-r(mu_2)), reps(100) strata(Index) : ttest Mod,
by(Index) unequal
(running ttest on estimation sample)
............................ end example........................

HTH and Kind Regards,
Carlo
-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Hugh Robinson
Inviato: giovedì 30 aprile 2009 4.09
A: statalist@hsphsun2.harvard.edu
Oggetto: st: permute test statistic

Can anyone tell me how to code permute properly to test if one modeled
growth rate (mod1) is greater than another (mod2).
Variations on the code below give me a perfect p-value each time.  It
seems that I have to substitute something else for "mean" to come up
with the proper test statistic?

permute  Mod1 mean=r(mean), reps(200) right nodots nodrop nowarn:
summarize Mod2


An example of the data is below.

Row	Mod1		Mod2
1	1.113924	.7163003
2	1.122969	.7857646
3	1.057594	.7346777
4	1.153763	.8520272
5	1.148739	.8732744
6	.9890202	.7147149
.
.
.
1000	1.193932	.9315556


Thanks,
HR

Hugh S Robinson Ph.D.
Postdoctoral Researcher
Wildlife Biology Program
College of Forestry and Conservation
University of Montana
Missoula, MT 59802
(406) 243-2931


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