Nothing wrong with Observational Studies. And Association does Imply Causality but…
Posted: June 19, 2011 by rdfeinman in Association and Causality, Evidence Based Medicine, Intention to Treat, low-carbohydrate diet, Observational Studies, thermodynamicsTags: low carbohydrate, red meat,, statistics
…the association has to be strong and the causality has to be plausible and consistent. And you have to have some reason to make the observation; you can’t look at everything. And experimentally, observation may be all that you have — almost all of astronomy is observational. Of course, the great deconstructions of crazy nutritional science — several from Mike Eades blog and Tom Naughton’s hysterically funny-but-true course in how to be a scientist – are still right on but, strictly speaking, it is the faulty logic of the studies and the whacko observations that is the problem, not simply that they are observational. It is the strength and reliability of the association that tells you whether causality is implied. Reducing carbohydrates lowers triglycerides. There is a causal link. You have to be capable of the state of mind of the low-fat politburo not to see this (for example, Circulation, May 24, 2011; 123(20): 2292 – 2333).
It is frequently said that observational studies are only good for generating hypotheses but it is really the other way around. All studies are generated by hypotheses. As Einstein put it: your theory determines what you measure. I ran my post on the red meat story passed April Smith and her reaction was “why red meat? Why not pancakes” which is exactly right. Any number of things can be observed. Once you pick, you have a hypothesis.
