Causal analyses of existing databases: no power calculations required

Observational databases are often used to study causal questions. Before being granted access to data or funding, researchers may need to prove that "the statistical power of their analysis will be high." Analyses expected to have low power, and hence result in imprecise estimates, will not be approved. This restrictive attitude towards observational analyses is misguided. A key misunderstanding is the belief that the goal of a causal analysis...