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	<title>Comments on: Multivariate Calibration</title>
	<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/</link>
	<description>Everyone knows how to average</description>
	<pubDate>Mon, 01 Dec 2008 18:58:07 +0000</pubDate>
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		<title>By: uced</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-154</link>
		<dc:creator>uced</dc:creator>
		<pubDate>Mon, 28 Apr 2008 19:04:23 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-154</guid>
		<description>Interesting point, Marty. Need to think about that. My Eq. 3a equals Brown87 Eq. 2.12, with text 'the maximum likelihood estimator of B from the calibration training data solely.' Some possibly relevant comments:

Indeed, there is assumption of no serial correlation, but errors can be correlated between responses. Yet, this correlation is to be estimated (after computing [tex]\hat{B}[/tex] ) so it cannot be used before.

CCE is not ML estimator, Sunberg99:

&lt;blockquote&gt;The classical estimator is not ML (unless q=p). Heuristically this is because only p-vector part of the q-vector is used for estimation of the unknown x, and the remaining q-p components contain some (little) information about [tex]\Gamma[/tex]
&lt;/blockquote&gt;




Brown87: Confidence and Conflict in Multivariate Calibration, Philip J. Brown; Rolf Sundberg; Journal of the Royal Statistical Society. Series B (Methodological), Vol. 49, No. 1. (1987), pp. 46-57.</description>
		<content:encoded><![CDATA[<p>Interesting point, Marty. Need to think about that. My Eq. 3a equals Brown87 Eq. 2.12, with text &#8216;the maximum likelihood estimator of B from the calibration training data solely.&#8217; Some possibly relevant comments:</p>
<p>Indeed, there is assumption of no serial correlation, but errors can be correlated between responses. Yet, this correlation is to be estimated (after computing <img src='/wp-content/plugins/wp-latexrender/pictures/40ecbaa26d22c1a0a4ab8103dea95ce9.gif' title='\hat{B}' alt='\hat{B}' align=absmiddle/> ) so it cannot be used before.</p>
<p>CCE is not ML estimator, Sunberg99:</p>
<blockquote><p>The classical estimator is not ML (unless q=p). Heuristically this is because only p-vector part of the q-vector is used for estimation of the unknown x, and the remaining q-p components contain some (little) information about <img src='/wp-content/plugins/wp-latexrender/pictures/07710b5c43702a8bb7b9104eacc6ba71.gif' title='\Gamma' alt='\Gamma' align=absmiddle/>
</p></blockquote>
<p>Brown87: Confidence and Conflict in Multivariate Calibration, Philip J. Brown; Rolf Sundberg; Journal of the Royal Statistical Society. Series B (Methodological), Vol. 49, No. 1. (1987), pp. 46-57.</p>
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		<title>By: Marty Ringo</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-153</link>
		<dc:creator>Marty Ringo</dc:creator>
		<pubDate>Thu, 24 Apr 2008 16:32:32 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-153</guid>
		<description>UCED,

I may not understand the initial setup, but equation system (1) appears to be just a system of q equations with the same exogenous variables in each equation, a "reduced form" system in the terminology of econometrics.  The estimator of alpha and B in (3a) and (3b) is like an OLS.  I am not clear here why the vectors of ones is not just placed in the "X" and standard notation used, but that is not my real question.

My problem comes from the G and the maximum likelihood estimator.  Is G diagonal?  If so, then I will trust you on the algebra for the rest.  But if G is not diagonal, i.e. not known to be diagonal apriori, then (3a) isn't the ML estimator of B.

Let me restate my question in the time dimension and equation dimension.  As I understand, we are assuming no serial correlation, and thus the covariance matrix for each equation is diagonal.  But what about between equations?  If there is correlation of the error terms between equations -- known in econometrics as a system of "Seemingly Unrelated Regression," or SUR, equations -- then that information would be in the likelihood function (the covariance of the i_th error term in equation k with the i_th error term in equation k').  

Further, while I am decades out of date with the research, I don't believe the finite sample distribution of SUR estimators for non-orthogonal regressors has been reduced to a tractable form and incorporated into the standard statistical software.  Now it may be that the inverse estimation problem is more tractable although that is not likely, and thus, I don't think that those F-statistics can be anything more than an approximation to the critical regions.  

Since the proxies are the original dependents, I can't say as to whether or not one can hypothesize zero cross-equation correlation, but with temperatures themselves the cross-equation (geographical correlation) is not zero (although a SUR, with ARMA, estimation of temperature doesn't offer much more than a standard, one-equation ARMA estimation).</description>
		<content:encoded><![CDATA[<p>UCED,</p>
<p>I may not understand the initial setup, but equation system (1) appears to be just a system of q equations with the same exogenous variables in each equation, a &#8220;reduced form&#8221; system in the terminology of econometrics.  The estimator of alpha and B in (3a) and (3b) is like an OLS.  I am not clear here why the vectors of ones is not just placed in the &#8220;X&#8221; and standard notation used, but that is not my real question.</p>
<p>My problem comes from the G and the maximum likelihood estimator.  Is G diagonal?  If so, then I will trust you on the algebra for the rest.  But if G is not diagonal, i.e. not known to be diagonal apriori, then (3a) isn&#8217;t the ML estimator of B.</p>
<p>Let me restate my question in the time dimension and equation dimension.  As I understand, we are assuming no serial correlation, and thus the covariance matrix for each equation is diagonal.  But what about between equations?  If there is correlation of the error terms between equations &#8212; known in econometrics as a system of &#8220;Seemingly Unrelated Regression,&#8221; or SUR, equations &#8212; then that information would be in the likelihood function (the covariance of the i_th error term in equation k with the i_th error term in equation k&#8217;).  </p>
<p>Further, while I am decades out of date with the research, I don&#8217;t believe the finite sample distribution of SUR estimators for non-orthogonal regressors has been reduced to a tractable form and incorporated into the standard statistical software.  Now it may be that the inverse estimation problem is more tractable although that is not likely, and thus, I don&#8217;t think that those F-statistics can be anything more than an approximation to the critical regions.  </p>
<p>Since the proxies are the original dependents, I can&#8217;t say as to whether or not one can hypothesize zero cross-equation correlation, but with temperatures themselves the cross-equation (geographical correlation) is not zero (although a SUR, with ARMA, estimation of temperature doesn&#8217;t offer much more than a standard, one-equation ARMA estimation).</p>
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		<title>By: uced</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-148</link>
		<dc:creator>uced</dc:creator>
		<pubDate>Thu, 10 Apr 2008 06:38:10 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-148</guid>
		<description>Walid,

1) http://www.climateaudit.org/pdf/statistics/brown.1982.jrss.pdf

2,3) I have only paper copies of those</description>
		<content:encoded><![CDATA[<p>Walid,</p>
<p>1) <a href="http://www.climateaudit.org/pdf/statistics/brown.1982.jrss.pdf" rel="nofollow">http://www.climateaudit.org/pdf/statistics/brown.1982.jrss.pdf</a></p>
<p>2,3) I have only paper copies of those</p>
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		<title>By: walid</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-124</link>
		<dc:creator>walid</dc:creator>
		<pubDate>Tue, 11 Mar 2008 16:14:25 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-124</guid>
		<description>Hi,

I' am Walid. I'm working on multivariate calibration and intervals calibration. I m needing copies of the following  3 articles:

1- Brown 82: Multivariate Calibration, Journal of the Royal Statistical Society. Ser B. Vol. 44, No. 3, pp. 287-321

2- Williams 69: Regression methods in calibration problems. Bull. ISI., 43, 17-28

3 -Krutchkoff 67: Classical and inverse regression methods of calibration. Technometrics, 9, 425-439..


Please contact me on: walidgani@yahoo.fr</description>
		<content:encoded><![CDATA[<p>Hi,</p>
<p>I&#8217; am Walid. I&#8217;m working on multivariate calibration and intervals calibration. I m needing copies of the following  3 articles:</p>
<p>1- Brown 82: Multivariate Calibration, Journal of the Royal Statistical Society. Ser B. Vol. 44, No. 3, pp. 287-321</p>
<p>2- Williams 69: Regression methods in calibration problems. Bull. ISI., 43, 17-28</p>
<p>3 -Krutchkoff 67: Classical and inverse regression methods of calibration. Technometrics, 9, 425-439..</p>
<p>Please contact me on: <a href="mailto:walidgani@yahoo.fr">walidgani@yahoo.fr</a></p>
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		<title>By: uced</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-29</link>
		<dc:creator>uced</dc:creator>
		<pubDate>Thu, 24 Jan 2008 09:08:49 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-29</guid>
		<description>"can you number your equations?"

Done.</description>
		<content:encoded><![CDATA[<p>&#8220;can you number your equations?&#8221;</p>
<p>Done.</p>
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		<title>By: John Creighton</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-28</link>
		<dc:creator>John Creighton</dc:creator>
		<pubDate>Thu, 24 Jan 2008 03:05:12 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-28</guid>
		<description>Hey UC,
can you number your equations? It makes them easier to refer to. It wasn't apparent to me until today that if X is a column vector then X' is a scalar. Thus it should be easy to minimize the above equation. That said it is not clear to me why the above error bounds are still valid for when x' is not scalar.</description>
		<content:encoded><![CDATA[<p>Hey UC,<br />
can you number your equations? It makes them easier to refer to. It wasn&#8217;t apparent to me until today that if X is a column vector then X&#8217; is a scalar. Thus it should be easy to minimize the above equation. That said it is not clear to me why the above error bounds are still valid for when x&#8217; is not scalar.</p>
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		<title>By: uced</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-26</link>
		<dc:creator>uced</dc:creator>
		<pubDate>Wed, 23 Jan 2008 13:04:35 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-26</guid>
		<description>John, "Also why is it that in the second equation on the page the transpose of X is taken but the transpose of X is not taken in the first equation on the page?"

The second equation corresponds to one new observation Y' (row vector), which doesn't belong to calibration data. X'  is transposed in the original Brown's text (xi in 2.2), I guess the reason is to
have unknown vector X' ( to be estimated) in column vector form.</description>
		<content:encoded><![CDATA[<p>John, &#8220;Also why is it that in the second equation on the page the transpose of X is taken but the transpose of X is not taken in the first equation on the page?&#8221;</p>
<p>The second equation corresponds to one new observation Y&#8217; (row vector), which doesn&#8217;t belong to calibration data. X&#8217;  is transposed in the original Brown&#8217;s text (xi in 2.2), I guess the reason is to<br />
have unknown vector X&#8217; ( to be estimated) in column vector form.</p>
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		<title>By: John Creighton</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-25</link>
		<dc:creator>John Creighton</dc:creator>
		<pubDate>Wed, 23 Jan 2008 05:34:22 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-25</guid>
		<description>Also why is it that in the second equation on the page the transpose of X is taken but the transpose of X is not taken in the first equation on the page?</description>
		<content:encoded><![CDATA[<p>Also why is it that in the second equation on the page the transpose of X is taken but the transpose of X is not taken in the first equation on the page?</p>
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		<title>By: John Creighton</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-24</link>
		<dc:creator>John Creighton</dc:creator>
		<pubDate>Wed, 23 Jan 2008 05:32:06 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-24</guid>
		<description>How come in the equation for the confidence interval that the B and X are in the opposite multiplicative order as in the original model?</description>
		<content:encoded><![CDATA[<p>How come in the equation for the confidence interval that the B and X are in the opposite multiplicative order as in the original model?</p>
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		<title>By: John Creighton</title>
		<link>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-23</link>
		<dc:creator>John Creighton</dc:creator>
		<pubDate>Wed, 23 Jan 2008 05:21:03 +0000</pubDate>
		<guid>http://signals.auditblogs.com/2007/07/05/multivariate-calibration/#comment-23</guid>
		<description>You must think I can't reading. I noticed you wrote something like I mentioned above. Anyway, let me try to minimize the left hand side as you say.</description>
		<content:encoded><![CDATA[<p>You must think I can&#8217;t reading. I noticed you wrote something like I mentioned above. Anyway, let me try to minimize the left hand side as you say.</p>
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