Witness A: "I'm not sure it was the defendant I saw pouring toxic in the lake, but I suppose if I had to guess I'd say it was. "
[Exit witness, who backstage puts on a lab coat and glasses, then returns to the witness box]
Witness B: "There's a statistically significantly greater probability that the defendant did it than that she did not. I'd stake my reputation as Dean of Harvard on those numbers."
Observation: B sounds more persuasive than A
Diagnosis: We conflate statistical confidence with personal confidence. When someone knows exactly how unsure they are, we see them as confident. Note though that the Dean didn't wager so much as a tuna sandwich on the defendant being guilty.
Tuesday, December 13, 2005