選擇與意向

記得以前有位同事找到新工作,可是他拿不定主意,問我有什麼意見。我問他為甚麼煩惱,他給了我很多理由,但我覺得那些理由無關痛癢,似乎他另有打算。於是我問他:你的理想職業為何?

他答道:我想幹有關環保的行業。〔他的本科跟生物、化學等理科相關〕

我追問道:很明顯,你現在的崗位跟環保沒關係。而且你新工作也跟環保沒關係。你說怎麼樣?

他回答:所以我就不知道該怎樣做。

我:新工作的前景如何?

他:底薪$13,000 , 頂薪$18,000。 〔那是政府工來的。薪金以月薪計算,下同〕

我:那比你現在的好一點。

他:不就是嘛。

我:那你為甚麼猶豫呢?

他:我還是喜歡環保多一點。

我:我知道你之前申請了另一份工,也是跟環保工作無關的。你又怎樣看?

他:那份工很高薪嘛,頂薪可以超過$35,000。

我:那即是說,如果那份高薪職業選中你,你就會放棄環保事業了,對嗎?

他:對。那當然啦。

我:那就好辦了。環保事業於你心目中的位置,不足$35,000,但卻比$18,000多一點。

$18,000 < 環保事業 < $35,000

他:唔。也可以這樣說。

我:不過我要強調,這只是你個人的主觀的衡量,跟現實未必有關係。如果有客觀數據,應該用客觀數據作準。

主人公最後沒有選那份$18,000的工作。過了一段時間,$35,000那份工作選了他。於是他的問題就完滿解決了。

其實我並不是隨便問那些問題。那段時期我看書讀到下面的一段:

Bruno de Finetti (1906-1985), The de Finetti Game
The de Finetti game consists of asking your friend a series of questions aimed at assessing his true subjective probability for the event of acing the test. Here’s how it works:

Tell your friend the following. “Let’s play a game. You have a choice. You can either draw a ball from a bag that has ninety-eight red balls and two black balls. If you happen to draw a red ball, I will give you one million dollars. Or you can decide to wait to see how you did on the test, and if you receive a perfect score on that test I will give you one million dollars. What’s your choice: draw or wait?"

Presumably, your friend will say, “Draw from the bag." If he doesn’t, it means he really has a subjective probability of one hundred percent of acing the test. If your friend’s decision is “draw", you ask the next question: “Now there are eighty red balls in the bag and twenty black ones. Do you want to draw, and if you obtain a red ball get a million dollars, or wait to see how you did on the test and get a million if you aced it?" If the answer is now “wait" (for the test result), then we know the subjective probability of acing the test is more than eighty percent but less than ninety-eight percent. So now choose some value in between, such as ninety percent and say: “Now there are ninety red balls and ten black ones in the bag, do you want to draw or wait?"If the answer is draw, try the next question: “There are eighty-five red balls and fifteen black ones, draw or wait?"If the answer is “Draw", try eighty-three red balls. Your friend’s answer now might be “I’m in different between drawing and waiting". In this case, the subjective probability of acing the test is eighty-three percent. If not, update the numbers of red and black balls in the bag accordingly so that you can bracket the actual subjective probability between a draw and a wait answer. (P.22-24)

Chance: A guide to gambling, love, the stock market and just about everything else / Amir D. Aczel. -[1st ed.] -London: High Stakes, 2005. – xiii, 160 p. : ill. ; 19 cm.

ISBN 1843440229

簡單點說,就是靠比較同一個人的不同選擇,從而確定他心裡面的主觀機會率。

只有觀察選擇的結果,我們才能了解人的真正意向。拒絶選擇,當事人未必是拿不定主意,說不定他是拒絕面對自己的真正意向。在市場經濟裡,沒有交易,我們就不知市價。在個人層面來說,不作選擇,我們就不知道自己真正作乎什麼。

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