In epidemiology, we are typically trying to estimate an unbiased measure of associations between an exposure and an outcome. Generally, we punt on the causal question of "does exposure X cause outcome Y?", but it is inevitably in the background. After all, if we say that poor exercise habits are associated with early mortality it is generally taken as an advisory to consider improving one's exercise habits rather than as an interesting coincidence.
But not all models are confounding models and the instincts that serve us so well for confounding models can be misleading for predictive models. Nate Silver has a very well explained example of how inaccurate (or, to be more formal, imprecise) predictive models can be worse than biased models. It's a very interesting confusion between bias and precision but it makes me wonder if we don't focus too much on unbiased and too little on efficiency for some of our models.
Links for 09-30-16
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