A Review Of The Rahn-Sturdivan Approach
We have now established that this article got the wrong answer because it relied too much on metallurgical speculation and didn't use available data to check itself. Here we review the major alternative approach, the steps taken by Rahn and Sturdivan in their two papers of 2004, and show how they differ from the metallurgical approach.
(1) Note that the five fragments fell into two
well-defined groups (by their antimony concentrations), both in the FBI's runs
in 1964 and Dr. Guinn's runs in 1977 (which used different pieces of the
(2) Use the General Linear Model on run 4 of the FBI's data to determine that the chance of these groups arising randomly from five bullets or planted samples fell between one in ten thousand and one in a hundred thousand. (In other words, the groups are not random.)
(3) Use Guinn's data from the 14 test bullets to establish that the antimony (from the four production runs grouped together) is distributed log-normally.
(4) Note that the antimony from the individual production runs shows indistinguishable distributions—the four lots were the same. (Among other things, this shows that the 14 bullets were effectively random samples of the four production runs.)
(5) Use the combined log-normal distribution to calculate the probability that any one of the fragments in the groups might have arisen by chance (from a third bullet or a planted fragment), and get 2% to 3%. (In other words, that didn't happen, either.)
(6) Use the resulting genuineness of the groups to derive other important conclusions (no conspiracy involving a second gunman that hit either of the men, the fragments not planted, Oswald's rifle fired that day, location of rear had wound rendered irrelevant, location of back wound rendered irrelevant, best shooting scenario provided, and the NAA serving as Rosetta Stone for the assassination by tying together the core physical evidence).
Note how this approach maximizes the use of available data and minimizes assumptions and theoretical constructs. It is as grounded as humanly possible. Given its strong results and implications, it is no wonder that so many JFK conspiracists have come out of the woodwork to attack it. Yet so far, no one has managed to touch it, in spite of all the heavy rhetoric to the contrary.
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