# st: RE: RE: unpaired regression

 From "Wallace, John" To "'statalist@hsphsun2.harvard.edu'" Subject st: RE: RE: unpaired regression Date Mon, 10 May 2004 22:07:51 -0700

```Doesn't that imply a relationship between the observations though?  Wouldn't
it be equally valid to end up with them lined up like
+-------------------------+
| batch   assay1   assay2 |
|-------------------------|
1. | Btch1     5400     .905 |
2. | Btch1     5320     .898 |
3. | Btch1     5670     .9   |
4. | Btch2     8600     .943 |
5. | Btch2     7840     .955 |
6. | Btch2     7550     .962 |

In the original line-up, the coefficient of determination is 0.968.  In the
second one above, its 0.8.

-----Original Message-----
From: Scott Merryman [mailto:smerryman@kc.rr.com]
Sent: Monday, May 10, 2004 6:42 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: unpaired regression

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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```