I would guess it would be something with an obvious confounding variable that you’ve forgotten to factor out. e.g. the “fluoride causes false teeth” example is pretty good for that, but is maybe not quite intuitive enough for what you’re looking for.
I would guess it would be something with an obvious confounding variable that you’ve forgotten to factor out. e.g. the “fluoride causes false teeth” example is pretty good for that, but is maybe not quite intuitive enough for what you’re looking for.