"This is a randomised clinical trial which is the gold standard for producing evidence, " she added.

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The researchers at Harvard couldn't run a randomised controlled trial where half the participants ate burgers for two decades and the other half didn't, but they could use statistical techniques as the next best thing.

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We've learnt from the lessons of the Randomised Badger Culling Trial and turned it into a policy that can be delivered and gives us the benefits of culling in the long term.

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The ScanBrit randomised, controlled, single-blind study of a gluten- and casein-free dietary intervention for children with autism spectrum disorders.

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They found that observational studies showed a 38% reduced risk of colorectal cancer, matching well to the 42% reduction shown by randomised trials.

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But the major UK investigation, the Randomised Badger Culling Trial (also called the Krebs trial), showed culling only produced a benefit if conducted rigorously and systematically over large areas, ideally with hard boundaries that badgers could not cross.

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