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<p class="MsoPlainText">Sorry about that<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">CoV Coefficient of Variation. It is the Standard Deviation (SD) divided by the Mean.<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">For example if the Mean (average) is 10 and the Standard Deviation is ±1 (also the value Sigma 1, “<span style="font-family:"Tahoma",sans-serif">ó</span>1”) then the CoV is 1/10 = 0.1 x 100 = 10%<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Both the mean and the standard deviation are directly related to the values in the data so to get a statement about how ‘variable’ the results were, the SD is divided by the mean turning the deviation into a fraction of the value. This
is multiplied by 100 to get a % number.<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">The CoV for test results varies with the stove, the test protocol and the task completed during the test.
<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Something that is lacking from our conversation is the idea that some stoves are themselves variable in performance even if everything else is identical. The current analysis of results allows no room for product variability. I proposed
that the Sigma one value be deducted from the mean before reporting the performance. This addresses issues related to the test method and the product, either of which may result in variation in the result.<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">The idea that a stove should be tested until the CoV meets a certain value ignores the possibility that the stove itself is simply a variable product. This is another misconception that has to be addressed by a future and acceptable
international standard.<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Regards<o:p></o:p></p>
<p class="MsoPlainText">Crispin<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"><span lang="EN-US" style="mso-fareast-language:EN-CA">-----Original Message-----<br>
From: Stoves [mailto:stoves-bounces@lists.bioenergylists.org] On Behalf Of Andrew Heggie<br>
Sent: 28-Jan-17 18:34<br>
To: Discussion of biomass cooking stoves <stoves@lists.bioenergylists.org><br>
Subject: Re: [Stoves] Sets of tests and the CoV of results - various methods</span></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Crispin am I the only one who stumbled over comprehending CoV probably meant covariance?<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Andrew<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">_______________________________________________<o:p></o:p></p>
<p class="MsoPlainText">Stoves mailing list<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">to Send a Message to the list, use the email address <a href="mailto:stoves@lists.bioenergylists.org">
<span style="color:windowtext;text-decoration:none">stoves@lists.bioenergylists.org</span></a><o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
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<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">for more Biomass Cooking Stoves, News and Information see our web site:<o:p></o:p></p>
<p class="MsoPlainText"><a href="http://stoves.bioenergylists.org/"><span style="color:windowtext;text-decoration:none">http://stoves.bioenergylists.org/</span></a><o:p></o:p></p>
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