It is instructive to consider cases in which most people readily accept causal claims in the absence of randomized experiments. Nowadays, few people doubt the effects of tobacco smoking on lung cancer. But in the 1950s, tobacco lobbyists embraced the idea that a genetic predisposition caused both a tendency to smoke and lung cancer … In other words, they claimed that there was an unblocked backdoor path. This idea was dispelled not by randomized, controlled experiments in humans, but by highly consistent results of observational studies using various controls and different sampling designs, experimental evidence from rodent studies, and demonstration of a plausible mechanism … A plausible mechanism is also what greatly increases scientists’ confidence in the causal effect
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Lars Pålsson Syll considers the following as important: Statistics & Econometrics
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It is instructive to consider cases in which most people readily accept causal claims in the absence of randomized experiments. Nowadays, few people doubt the effects of tobacco smoking on lung cancer. But in the 1950s, tobacco lobbyists embraced the idea that a genetic predisposition caused both a tendency to smoke and lung cancer … In other words, they claimed that there was an unblocked backdoor path. This idea was dispelled not by randomized, controlled experiments in humans, but by highly consistent results of observational studies using various controls and different sampling designs, experimental evidence from rodent studies, and demonstration of a plausible mechanism …
A plausible mechanism is also what greatly increases scientists’ confidence in the causal effect of human activity on the climate: Human activity, such as industrial processes, increases the atmospheric concentrations of greenhouse gases. Atmospheric greenhouse gases, in turn, warm the Earth’s surface through an uncontroversial mechanism, the greenhouse effect … And a plausible mechanism is also the reason why one does not need randomized controlled trials to conclude that parachute use during free fall reduces mortality …