Probability distributions and writing style

by dclayh1 min read4th Jun 20098 comments


Personal Blog

In his recent post, rhollerith wrote,

I am more likely than not vastly better off than I would have been if <I had made decision X>

This reminded me of the slogan for the water-filtration system my workplaces uses,

We're 100% sure it's 99.9% pure!

because both sentences make a claim and give an associated probability for it. Now in this second example, the actual version is better than the expectation-value-preserving "We're 99.9% sure it's 100% pure", because the actual version implies a lower variance in outcomes (and expectation values being equal, a lower variance is nearly always better).  But this leads to the question of why rhollerith didn't write something like "I am almost certainly at least somewhat better off than I would have been...". 

So I ask: when writing nontechnically, do you prefer to give a modest conclusion with high confidence, or a strong conclusion with moderate confidence?  And does this vary with whether you're trying to persuade or merely describe?

(Also feel free to post other examples of this sort of statement from LW or elsewhere; I'd search for them myself if I had any good ideas on how to do so.)