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Re: st: Construct Null Datasets through Bootstrap Resampling


From   "Michael Blasnik" <michael.blasnik@verizon.net>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Construct Null Datasets through Bootstrap Resampling
Date   Fri, 01 Dec 2006 00:26:18 -0500

One more difference between the approaches that you should recognize is that bsample samples with replacement (a value from a given observation can appear more than once) while the scramble program I wrote does not -- it simply re-arranges the order. I'm not sure which is preferred for your application.

If you end up wanting to sample without replacement (as scramble does) but want to keep groups of variables together, a relatively modest change to the scramble code would do the trick.

Michael Blasnik

----- Original Message ----- From: "Erik Ingelsson" <Erik.Ingelsson@pubcare.uu.se>
To: <statalist@hsphsun2.harvard.edu>
Sent: Thursday, November 30, 2006 11:37 PM
Subject: Re: st: Construct Null Datasets through Bootstrap Resampling



Dear Austin,

Well, actually Michael Blasniks suggestion was a bit closer to what I first intended. But when looking at your suggestion and reading some literate on multiple testing in genetic analyses, I realized that I actually perhaps should not scramble all variables, but rather keep them together in two groups (e.g. keeping var 1-4 togeter as in the orignal observation, but randomly pairing them with var 5-8). For this, your solution worked perfectly. The next step is to meet with our senior statistician and show him what I got. He can tell which way to go, I hope.

Thanks a lot to both of you! I am impressed by the fast answers!
Erik Ingelsson
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