Converting Ordinary Language to Probabilities: CIA Edition, by Bryan Caplan

Interesting email from Todd Proebsting, reprinted with his permission.

Dear Prof. Caplan,

Your recent attempt at a wager on Iran's nuclear progress,
and the subsequent exchange with the author about why you wanted 10:1 odds
reminded me that the CIA tried to quantify what certain claims meant:

100% Certainty

The General Area of Possibility

93%

give or take about 6%

Almost certain

75%

give or take about 12%

Probable

50%

give or take about 10%

Chances about even

30%

give or take about 10%

Probably not

7%

give or take about 5%

Almost certainly not

0% Impossibility

 

It's from a 50-year old CIA proposal.

 

It's interesting to me that "Almost certain" was
only 93%.  I think the CIA would have argued that you should have been asking
for even longer odds given the original claim.

Cheers, Todd
Proebsting

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