[pbourke]

> The study results are "colonoscopies do not lead to a reduction in colon cancer mortality". Reporting that isn't misleading that's what the study says.

The measured intervention was not the colonoscopy, it was the invitation to screen. Only 42% of invited patients actually got a colonoscopy. This is far more persuasive to me:

> "When the investigators compared just the 42% of participants in the invited group who actually showed up for a colonoscopy to the control group, they saw about a 30% reduction in colon cancer risk and a 50% reduction in colon cancer death. “That adds to a bunch of observational study data that suggests exposing people to colonoscopy can reduce risk of developing and dying of colon cancer,” Gupta said."

As a member of the public, I don't really care about invitation to screen, but do care about the efficacy of colonoscopy. I can see invitation to screen being an important concern from a public health standpoint.

[JamesBarney]

The problem is whether or not they chose to get a colonoscopy is a confounding variable which inflates the value of the colonoscopy when some of the results are driven by other attributes.