Monty Hall problem 1.4.2

Frequency probability and Bayesian probability, 3.2.2

機會率哲學 3.2.2

這段改編自 2010 年 4 月 3 日的對話。

「頻率學派」和「貝葉斯學派」之中,究竟哪一個正確呢?又或者說,哪一個較為有用呢?

「機會率」既有客觀的成份,又有主觀的成份。留意,這裡「主觀」的意思,並不代表「不正確」。一方面,我們真的使用「機會率」,來描述外在事件;另一方面,「機會率」又真的會反映,一個人對一件外在事件的結果,無知程度的深淺。

「機會率」處理「未知」,但不一定處理「未來」,因為「未知」不一定代表「未來」。例如,剛才的例子中,骰子已擲,而我亦知道了結果,所以不是「未來」。但是,因為你還未看結果,所以相對你來說,那仍然是「未知」。你仍然需要使用「機會率」,來估計結果。大概而言,所有人也不知的,為之「未來」;精確而言,尚未發生的,才為之「未來」。

對於「機會率真義」這個問題,我的第一個解答是,其實「頻率學派」所講的「機會率」,和「貝葉斯學派」所講的「機會率」,根本是兩個不同的概念,有著不同的意思,雖然兩個意思十分相關,相關到會用同一個名字「機會率」,甚至很多時會有相同的數值。

既然是兩個不同的概念,我們何不索性賦予它們,兩個不同的名字。那就可以避免再混淆。我們可以把「頻率學派」的「機會率」,叫做「頻率機會率」、「客觀機會率」,或者「物理機會率」。然後,我們把「貝葉斯學派」的「機會率」,叫做「貝葉斯機會率」、「主觀機會率」,或者「知識機會率」。

— Me@2012.11.23

2012.11.23 Friday (c) All rights reserved by ACHK

Superdeterminism

Paradox 9

In the context of quantum mechanics, superdeterminism is a term that has been used to describe a hypothetical class of theories which evade Bell’s theorem by virtue of being completely deterministic. Bell’s theorem depends on the assumption of [non-] counterfactual definiteness, which technically does not apply to deterministic theories. It is conceivable, but arguably unlikely, that someone could exploit this loophole to construct a local hidden variable theory that reproduces the predictions of quantum mechanics.

… in a deterministic theory, the measurements the experimenters choose at each detector are predetermined by the laws of physics. It can therefore be argued that it is erroneous to speak of what would have happened had different measurements been chosen; no other measurement choices were physically possible. Since the chosen measurements can be determined in advance, the results at one detector can be affected by the type of measurement done at the other without any need for information to travel faster than the speed of light.

— Wikipedia on Superdeterminism

Even if there are no other physical possibilities for a measurement choice, there are other logical possibilities. The goal of quantum mechanics, or science in general, is to consider, for an identical system, what input results what output.

The problem of superdeterminism in quantum mechanics is not “claiming the observers’ action are deterministic”, but by claiming so, claiming also that there is no decoherence (wave function collapse).

When we say that the observer cannot be separated from the observed, we mean that we have to consider the whole (observed + observer), instead of shifting the system from the observed to the observer, and then ignoring the original observed itself.

— Me@2012-11-20 02:11:06 PM

2012.11.23 Friday (c) All rights reserved by ACHK