Probability

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{{wp|Probability|Probability}}
 
{{wp|Probability|Probability}}
Probability is the knowledge or belief that how likely something is going to happen.
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'''Probability''' is the analysis of how likely or unlikely something is.
  
 
==Used by creationists==
 
==Used by creationists==

Revision as of 01:56, 11 April 2010

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There is a broader, perhaps slightly less biased, article on Wikipedia about Probability

Probability is the analysis of how likely or unlikely something is.

Contents

Used by creationists

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For those living in an alternate reality, Conservapedia has an "article" about Probability

Many of the nut jobs creation scientists and their related ilk, editors of Conservapedia, love to mention how so many of the things we observe around us have a probability of occurring of nearly zero. They love that "nearly zero" thing. They seem to believe that if the odds are low enough, then what we see couldn't have randomly happened. However, since we do observe the "whatever improbable thing", then it must have made it despite the odds.

Again, they always mention the "nearly zero" thing. Actually, they mean zero. They pretend to give the observation the however low probability that it might have, but they truly believe that it had zero probability. That is perfectly reasonable given that their solution is that the observed effect was created supernaturally. Since a supernatural occurrence does have a zero chance of probability, they are perfectly consistent in their beliefs.

Past, present, and future

One thing that needs to be understood by the creationists is that improbability is only of concern to future events. The improbability of an event is of no concern if the event has happened. In other words, applying probability to something that has already happened (i.e. the past) is meaningless. It IS, its probability of happening no longer matters.[1] The probability of the event occuring again is, however, valid.

A hypothetical example

As an example of the fallacy of looking at results and conjecturing backwards on what the probability of such occurring was, roll a die 200,000 times. (Don't really do this, you have better things to do with your time.) The results don't matter, but your probability of rolling whatever sequence of numbers were rolled is so small (Even rolling any specific sequence in ten rolls is something like 60 million to one) as to be practically zero (Not exactly zero for the reasons discussed in the section below). Yet you managed to do something that had a "nearly zero" probability of happening. Congratulations, you're magic - just like Jesus![2]

Zero probability

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There is a broader, perhaps slightly less biased, article on Wikipedia about Almost surely

There is a slight difference between "having a zero probability occuring" and "will never occur"

  • Something "will never occur" means there is no option for it to occur. For example, flip a fair edgeless coin and the event that "neither heads nor tails is flipped" will never occur given the coin only has heads or tails. No other option can be randomly generated.
  • Something "having a zero probability occuring" means there is, theoretically, no possibility of occurrence. For example, if a fair edgeless coin is thrown ad infinitum, theoretically one can obtain a sequence without ever having flipped a single tails (no laws are prohibiting against flipping tails or heads, so it is theoretically possible to keep flipping heads). the actual probability of having no tails flipped in the infinite sequence is exactly zero (\textstyle {\lim_{n \rightarrow \infty}\frac{1}{2^n}=0}). If the sequence is stopped at some point however, since the sequence is finite, the probability is no longer zero, however close it might be.

However, given two events A and B, the probability of A happening given B would be undefined if the probability of B is zero, directly result from the following formula in Bayesian probability:

P(A \mid B) = \frac{P(A \cap B)}{P(B)}\,

What this means is that it is impossible to determine the probability of A happening given B a priori if B has zero probability of occuring.

Other pitfalls

One of the pitfalls of using probability, especially for the realm of chemical reactions, is that it usually demonstrates the total lack of understanding of the actual mechanisms or it is under the unnecessary assumption of black box given the actual mechanisms haven been went over at various places like Talk Origins.

Footnotes

  1. Unless, of course, an alternative theory has a higher probability given all available data - which, of course, the supernatural certainly does not
  2. With apologies to Sarah Silverman.
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