Wednesday, December 14, 2011

Revealing ClimateGate email 4060: Warmist Ed Cook argues that a "double-blind" approach shouldn't be used in the proxy reconstruction game

Email 4060

Perhaps the biggest complaint I have with the PR Challenge is its "double-blind" design that gives the tester no information on the problem being tested even though no such situation ever occurs in practice. At that level alone, the "double-blind" design used in the PR Challenge is very odd. Regardless, I fully understand the value of "double-blind" statistical experiments as the only way to test for true causality in, for example, cancer drug tests. But this is simply not the kind of problem we are dealing with in the proxy reconstruction game (with all due respect to your statistician colleagues). We are much more involved in something more akin to epidemiological hypothesis testing on real pre-existing data, like the association between smoking and lung cancer in humans. Do medical epidemiologists perform "double-blind" experiments to determine if smoking causes lung cancer? Basically no. They use the data available to them to answer that hypothesis with a high degree of statistical certainty without the need to conduct "double-blind" experiments on humans (not possible for smoking and lung cancer in any case). So in my opinion, the "double-blind" approach is unnecessary and, I would argue, even inappropriate here. I also don't like it because that is not the way we should be conducting our science. When I worked with Keith and Phil for a month at CRU on our NATO test data sets and reconstruction methods, we worked in a completely objective and open way that enabled us to debate various options and interpretations of our programs and reconstructions. We were also able to thoroughly test our programs using identical data for the special case of full MLR. This enabled us to be absolutely certain that we could compare results in the various best-subset cases that are typically used for reconstructing climate from tree rings. There does not appear to be any such mechanism for doing so in your PR Challenge, so differences found may be as much related to odd programming matters rather than the methods being compared. In any case, comparison of reconstruction methods should be conducted openly and that is the way that I love to work. So if the "double-blind" requirement were removed from the PR Challenge, I would be much more inclined to participate. I am not adverse to being proven wrong (or "less right" perhaps) in an open environment that allows for direct "give-and-take" on the merits of the cases being tested and argued. A "double-blind" approach is explicitly designed to eliminate the scientific openness needed to evaluate and debate reconstruction methods in my opinion. At that level, and for reasons stated above, I reject it. Regards, Ed

Blind experiment - Wikipedia, the free encyclopedia

Double-blind methods can be applied to any experimental situation where there is the possibility that the results will be affected by conscious or unconscious bias on the part of the experimenter.

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