在一篇對證券分析師和氣象預測員做比較的論文中，Tadeusz
Tyszka 和 Piotr Zielonka
證實，分析師做得比較差，卻對自己的技能有較高的信心。不知為什麼，分析師的自我評估，並沒有在預測錯誤之後，降低他們的錯誤率。
Philip
Tetlock 也做了類似的研究。為了研究政治和經濟
『專家』的表現，他請了將近三百名專家，在某個指定期間內
( 大約是未來五年 )
判斷所發生的幾個政治、經濟、和軍事事件。他得到這些專家所做的大約八萬二千個預測。經濟學家佔了他樣本的四分之一。其研究顯示，專家的錯誤率顯然是他們自己所估計的好幾倍。他的研究暴露出一個專家問題：預測者是博士或學士，其結果並沒有差異。著作等身的教授並沒比新聞記者高明。Tetlock
所發現的唯一規律是，名望對預測有負面效果：名滿天下的人所做的預測比沒沒無聞者還差。
The
Good Judgment Project conducted by Philip E. Tetlock
從 1987 起, Tetlock 便開始就各種主題, 去收集各種政界和學界的專家所做的各式各樣的預測, 從內政、經濟到國際關係. Tetlock 當時在加州大學柏克萊分校擔任心理學與政治學教授, 他後來轉到賓夕法尼亞大學任教.
回覆刪除補充：
回覆刪除統計是一種用來印證道理 ----- 也就是事物間因果關係 ----- 的工具. 當事物之間有某種因果時, 統計可以協助你發現並且驗證這樣的關係, 進一步預測這個因果再次發生的機率. 相反的, 如果事物之間缺乏真實的因果, 則無論統計之後得到任何結論, 也只是數學上的巧合.
無論統計的結果如何, 如果你沒辦法找到它背後的道理, 那就代表這次的分析出了問題. 統計學的精髓在於 "以管窺天 ", 利用樣本的資料來做分析, 抽取有用的資訊, 做出 "精準的預測 ".
身處 " 巨量資料 " ( big data ) 的時代, 數據資料大量存在, 在日常生活中俯拾即是. 但是, 預測最難的部分在於：從巨量資料中分辨雜訊和真正的訊號. 而人們通常只選擇聽見對自己有利的數據, 錯把雜訊當成信號, 因而做出錯誤的判斷, 這就是為什麼有些預測會失敗, 而有些預測卻能與結果非常接近的主要原因.
[ Extracted from " Why the experts missed the crash " ]........( 1 )
回覆刪除What makes some forecasters better than others?
The most important factor was not how much education or experience the experts had but how they thought. You know the famous line that [philosopher] Isaiah Berlin borrowed from a Greek poet, "The fox knows many things, but the hedgehog knows one big thing"? The better forecasters were like Berlin's foxes: self-critical, eclectic thinkers who were willing to update their beliefs when faced with contrary evidence, were doubtful of grand schemes and were rather modest about their predictive ability. The less successful forecasters were like hedgehogs: They tended to have one big, beautiful idea that they loved to stretch, sometimes to the breaking point. They tended to be articulate and very persuasive as to why their idea explained everything. The media often love hedgehogs.
How do you know whether a talking head is a fox or a hedgehog?
Count how often they press the brakes on trains of thought. Foxes often qualify their arguments with "however" and "perhaps," while hedgehogs build up momentum with "moreover" and "all the more so." Foxes are not as entertaining as hedgehogs. But enduring a little tedium is worth it if you want realistic odds on possible futures.
So if you were looking for a money manager, you'd want a fox?
If you want good, stable long-term performance, you're better off with the fox. If you're up for a real roller-coaster ride, which might make you fabulously wealthy or leave you broke, go hedgehog.
But it was doomster hedgehogs like money managers Robert Rodriguez and Jeremy Grantham who first saw the crisis coming.
Hedgehogs are sometimes way, way out front. But they can also be way, way off.
[ Extracted from " Why the experts missed the crash " ]........( 2 )
回覆刪除Most of the experts who called the downturn are still bearish. Would you expect them to be able to call the rebound too?
No. In our research, the hedgehogs who get out front don't tend to stay out front very long. They often overshoot. For example, among the few who correctly called the fall of the Soviet Union were what I call ethno-nationalist fundamentalists, who believed that multi-ethnic nations were likely to be torn apart. They were spectacularly right with Yugoslavia and the Soviet Union. But they also expected Nigeria, India and Canada to disintegrate. That's how it is with hedgehogs: You get spectacular hits but lots of false alarms.
How can we nonexperts test our own hunches?
Listen to yourself talk to yourself. If you're being swept away with enthusiasm for some particular course of action, take a deep breath and ask: Can I see anything wrong with this? And if you can't, start worrying; you are about to go over a cliff.
Considering how wrong they are, why are the same old talking heads continuing to give advice?
Unless you force experts to be specific, as we did, they can make predictions that are difficult to falsify. You know the cynical clich "Never assign a date and a number to the same prediction." That lets you get away with saying things like "Yes, I did say the Dow will hit 36,000, and it will - just wait. I was merely a little early."
Experts are also very good at explaining errors away by concocting counterfactual history. "If only the world had heeded the warnings of, say, [libertarian-leaning Texas Congressman] Dick Armey about Fannie Mae and Freddie Mac, the financial crisis would have been far less severe." This is a ridiculous line of reasoning. Nobody knows what would have happened in a hypothetical world.
Who are you listening to in this market?
I look for a combination of cognitive flexibility and high IQ. Moody's Economy.com chief economist Mark Zandi is not a bad person to listen to. He was somewhat out in front in anticipating this crisis and has a capacity for seeing different points of view. Larry Summers, head of the National Economic Council, also has the kind of intelligence and cognitive style that makes him a good bet.
Could we live without experts?
No way. We need to believe we live in a predictable, controllable world, so we turn to authoritative-sounding people who promise to satisfy that need. That's why part of the responsibility for experts' poor record falls on us. We seek out experts who promise impossible levels of accuracy, then we do a poor job keeping score.