David Spiegelhalter over at Understanding Uncertainty is blogging about the latest CRIIGEN rat feeding study that was carried out with GM maize:
With others, I made some comments for the press about the recent paper (abstract, figures and tables freely available here) on cancer in rats fed GM maize and Monsanto's Roundup pesticide.
[ Full paper should also be available here].
Whatever the truth about GMOs, this is not a great contribution to the debate. The paper is not well written, to say the least, with phrases such as “In females, all treated groups died 2–3 times more than controls, and more rapidly” in the abstract. The Methods section gives a whole lot of detail about some complex secondary method, but nothing on the analysis of the primary outcome data, presumably tumour incidence over time.
If we assume the experiment was carried out appropriately, the crucial flaw was only having 20 control rats, 10 in each group, so that it is (predictably) almost impossible to show statistically significant differences, since the control rats would have been expected to develop tumours too. In fact no formal statistical tests are carried out, and one does not have to do much maths to understand that statements about ‘30% of male control rats’ actually mean ‘3 out of 10’...
@ Rats and GM | Understanding Uncertainty:
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