tag:blogger.com,1999:blog-31819641.post3685956235034086448..comments2023-10-06T03:21:26.130-07:00Comments on trust but verify: Idiots look at Data, Part III: Slightly closer lookDBrowerhttp://www.blogger.com/profile/17718913310467614671noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-31819641.post-51625220746390363482007-11-29T20:17:00.000-08:002007-11-29T20:17:00.000-08:00For the record, TbV, there is a reason given why t...For the record, TbV, there is a reason given why there is no value given for the 5aA in the July 3 test. On page 92 of exhibit 92, it says:<BR/><BR/>"NB: La valeur isotopique du 5aA n'a pu etre determinee en raison de sa faible concentration dans l'echantillon."<BR/><BR/>"Note bene: the isotopic value of 5aA was not determined for the reason of its weak concentration in the sample." <BR/><BR/>Not that it matters now. But I cannot see from exhibit 92 why it has any weaker concentration in the sample than in any other sample. It looks to me like they just couldn't decide if it was peak 14 or 15 in the July 3 IRMS 'gram, so they punted.Mike Solberghttps://www.blogger.com/profile/11784753552166129987noreply@blogger.comtag:blogger.com,1999:blog-31819641.post-88046317050458267782007-11-09T10:29:00.000-08:002007-11-09T10:29:00.000-08:00The goodness of a metric depends on what you are u...The goodness of a metric depends on what you are using it for, and how reliably it tracks what you are concerned about. I can accept that what I'm doing is not what M is immediately concerned about, but that is not my goal.<BR/><BR/>TBVDBrowerhttps://www.blogger.com/profile/17718913310467614671noreply@blogger.comtag:blogger.com,1999:blog-31819641.post-11389409527425504472007-11-09T09:20:00.000-08:002007-11-09T09:20:00.000-08:00TBV, One other thing. I don't think total peaks i...TBV, <BR/><BR/>One other thing. I don't think total peaks is a good metric. What we are concerned about is the noise around the metabolite peaks of interest. Noise far away doesn't affect our measurements.mhttps://www.blogger.com/profile/11845675234084955737noreply@blogger.comtag:blogger.com,1999:blog-31819641.post-59709131819482413372007-11-09T00:01:00.000-08:002007-11-09T00:01:00.000-08:00M, when I look at details, I think the Shackleton ...M, <BR/><BR/>when I look at details, I think the Shackleton chromatograms are still very much better, in a quantifiable way, that I'll be working through.<BR/><BR/>The observation on the UCLA slide is a point well taken, and I need to think about whether it affects my analysis. I think I am looking at a different kind of meta-analysis, and it may not matter, but I'm not sure.<BR/><BR/>TBVDBrowerhttps://www.blogger.com/profile/17718913310467614671noreply@blogger.comtag:blogger.com,1999:blog-31819641.post-1419531195128999372007-11-08T23:48:00.000-08:002007-11-08T23:48:00.000-08:00TBV,I think I figured it out.The UCLA slide is the...TBV,<BR/><BR/>I think I figured it out.<BR/><BR/>The UCLA slide is the etio and andro which elutes at about 1200+ seconds, etio followed by andro. This is the Landis F2. So you should compare the UCLA slide with the F2 graphs such as USADA 0343. <BR/><BR/>You will see that the andro and etio peaks while close together seem pretty well defined in the Landis F2 at USADA 0343. Yes there is a little more noise in areas away from the etio and andro, and one big peak following the andro. On the other hand blowup of the UCLA graph shows that the etio peak trails into the small following andro peak.<BR/><BR/>You should not be comparing the UCLA slide to the F3 graphs because it appears the 5B and 5A graphs are just more noisy, maybe because it's just harder to do the separation chemistry for those metabolites.<BR/><BR/>One proper comparison is the bottom graph in the Shackleton figure 3 above, which shows an intervening peak between the 5B and 5A and some possible shoulders. That's pretty messy by your criteria, yet Shackleton found it adequate for his carbon ratio calculations in his pioneering study. And I seem to recall Shackleton testified that the LNND chromatograms were fine.mhttps://www.blogger.com/profile/11845675234084955737noreply@blogger.com