Gauss defined what is normal. And yes not only behaviour also weight, height, hormone levels are subject to change and thus there is a new "normal" every now and then. Since this is statistics, normal...
You just made my whole point better than I did. Gauss gave us normal as a curve, and a curve moves with the crowd, which is exactly how smoking ended up normal. The older meaning comes from the carpenter's square, a standard you measure against. Smoking was normal by the curve the entire time it was wrong by the square. That gap is what the post is about.
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