In the late 1940s, the Communist government of Yugoslavia broke from the Soviet Union, raising fears that the Soviets would invade. In March 1951 [US intelligence under Sherman Kent reported there was a “serious possibility” of a Soviet attack.] But a few days later, Kent was chatting with a senior State Department official who casually asked, “By the way, what did you people mean by the expression ‘serious possibility’? What kind of odds did you have in mind?” Kent said he was pessimistic. He felt that the odds were about 65 to 35 in favor of an attack. The official was startled. He and his colleagues had taken “serious possibility” to mean much lower odds.Via Slate Star Codex
Disturbed, Kent went back to his team. They had all agreed to use “serious possibility” in the [report], so Kent asked each person, in turn, what he thought it meant. One analyst said it meant odds of about 80%. Another thought it meant odds of 20% – exactly the opposite. Other answers were scattered between those extremes. Kent was floored. A phrase that looked informative was so vague as to be almost useless…
In 1961, when the CIA was planning to topple the Castro government by landing a small army of Cuban expatriates at the Bay of Pigs, President John F. Kennedy turned to the military for an unbiased assessment. The Joint Chiefs of Staff concluded that the plan had a “fair chance” of success. The man who wrote the words “fair chance” later said he had in mind odds of 3 to 1 against. But Kennedy was never told precisely what “fair chance” meant and, not unreasonably, he took it to be a much more positive assessment.
Thursday, March 10, 2016
Words and Numbers
From Superforecasting: The Art and Science of Prediction, by Philip E. Tetlock and Dan Gardner: