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st: RE: unpaired regression


From   "Scott Merryman" <smerryman@kc.rr.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: unpaired regression
Date   Mon, 10 May 2004 20:41:46 -0500

How about lining up the measurements?

Something like

. l

     +-------------------------+
     | batch   assay1   assay2 |
     |-------------------------|
  1. | Btch1     5400        . |
  2. | Btch1     5320        . |
  3. | Btch1     5670        . |
  4. | Btch1        .       .9 |
  5. | Btch1        .     .905 |
     |-------------------------|
  6. | Btch1        .     .898 |
  7. | Btch2     8600        . |
  8. | Btch2     7840        . |
  9. | Btch2     7550        . |
 10. | Btch2        .     .962 |
     |-------------------------|
 11. | Btch2        .     .955 |
 12. | Btch2        .     .943 |
     +-------------------------+

. by batch: replace assay2 = assay2[_n +3]
(12 real changes made, 6 to missing)

. drop if assay1 == .
(6 observations deleted)

. l

     +-------------------------+
     | batch   assay1   assay2 |
     |-------------------------|
  1. | Btch1     5400       .9 |
  2. | Btch1     5320     .905 |
  3. | Btch1     5670     .898 |
  4. | Btch2     8600     .962 |
  5. | Btch2     7840     .955 |
     |-------------------------|
  6. | Btch2     7550     .943 |
     +-------------------------+


Scott

________________________________________
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Wallace, John
Sent: Monday, May 10, 2004 7:48 PM
To: 'statalist@hsphsun2.harvard.edu'
Subject: st: unpaired regression

I have two measures of batch performance on which I'd like to perform a
regression.  The measurements are taken on separate samples from the batch,
and typically look something like:
            Assay1 Assay2
Btch1    5400          
Btch1    5320          
Btch1    5670          
Btch1                0.900
Btch1                0.905
Btch1                0.898
Btch2    8600          
Btch2    7840          
Btch2    7550         
Btch2                0.962
Btch2                0.955
Btch2                0.943
...etc (on for multiple batches which show correlated measures for the two
assays)
-collapse- ing them to batch averages and then performing the regression is
one approach, but it doesn't take variance of the measures themselves into
account in the regression.  Is there a system for performing this type of
analysis?
 
Thanks,
John Wallace | Research Associate | Test Method Development
AFFYMETRIX, INC. | 3380 Central Expressway | Santa Clara, CA 95051 | Tel: 
408-731-5574 | Fax:  408-481-0435
 


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