Chance of Identical Numbers in Infinite Series

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    Infinite Probability
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Discussion Overview

The discussion revolves around the probability of selecting identical numbers from an infinite series or set. Participants explore concepts related to randomness, finite versus infinite sets, and the implications of choosing numbers at random from these sets. The conversation touches on theoretical aspects of probability, mathematical reasoning, and the nature of infinity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • Some participants question whether a "1 in infinity" chance constitutes a real chance at all, leading to discussions about the nature of zero and infinitesimal probabilities.
  • Others argue that if numbers are chosen from a finite set, such as between 0 and 10,000, the probability of selecting the same number is non-zero, specifically calculated as 1/10000^2.
  • A participant notes that the concept of "at random" typically implies a uniform distribution, which raises questions about the validity of the original question when applied to infinite sets.
  • Some contributions explore the implications of choosing from infinite sets, suggesting that the probability of selecting any specific number from an infinite set is zero, yet the probability of selecting a number from a defined range remains 1.
  • There are discussions about the nature of infinity, including the existence of bijections between different infinite sets, such as odd numbers and prime numbers, and how this relates to the concept of cardinality.
  • A participant shares a VBscript code to illustrate random selection, though its relevance to the theoretical discussion is unclear.

Areas of Agreement / Disagreement

Participants express differing views on the nature of probability in infinite versus finite contexts. While some agree on the non-zero probability in finite cases, others maintain that in infinite contexts, the probability of selecting the same number is effectively zero. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Limitations include the ambiguity in defining "random selection" and the implications of different mathematical frameworks (e.g., measure theory) that govern probabilities in infinite sets. The discussion also reflects varying interpretations of infinity and its properties.

Who May Find This Useful

This discussion may be of interest to those studying probability theory, set theory, or mathematical concepts related to infinity, as well as individuals curious about the philosophical implications of randomness and chance.

  • #31
VikingF said:
I think that's an ugly abuse of the probability 1. :smile:
You can't find probabilities that are larger than 1, but an event can SURELY :biggrin: be more certain than just "almost surely", if you see what I mean. :rolleyes:

Things can also "surely" happen. Consider the uniform distribution on the unit interval [0,1]. You will "almost surely" pick an irrational number. However, you will "surely" pick a real number.

You might want to look into measure theory if you want to try to understand the finer points behind probability theory. This is the stuff that they won't bother teaching your engineering stats class, but is really needed if you want to learn some rigorous probability and not just how to apply various distributions to bolts coming off an assembly line.
 
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  • #32
Discrete & Continuous random variables have different contexts. Discrete random variables coincide more with experience because we don't generally deal with infinite sample spaces in real life. With discrete random variables we assign probability 0 to events that we suppose will not happen, so it's only a discrepancy if we don't keep in mind that the context is different, so things have different meanings. Any time we are dealing with continuous random variables we should be aware that probability 0 doesn't mean the outcome is impossible, only that it is so small that it is irrelevant. Mostly a semantics issue.
 
  • #33
The answer to your questions is, YES. A chance is still a chance, even if it's a showball's chance in hell
 
  • #34
Serene_Chaos said:
Ok I am not sure if this is where this thread should go, but anyway.

My question is this:
if we have an infinite series of numbers (or apples, or whatever) and we choose one at random, and then choose another at random, is there a chance that the two will be the same? I mean, is a 1 in infinity chance a chance at all?

wcemichael said:
The answer to your questions is, YES. A chance is still a chance, even if it's a showball's chance in hell

The answer is the same as it was over 5 years ago. It is possible with a probability of zero. (That's not a contradiction).
 

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