Chance of Identical Numbers in Infinite Series

Click For Summary
In an infinite series of numbers, the probability of selecting two identical numbers is essentially zero when considering an infinite set, as choosing any specific number from an infinite set yields a probability of zero. However, when selecting from a finite set, such as numbers between 0 and 10,000, the probability of matching numbers is positive, calculated as 1/10,000^2. The discussion highlights the complexities of defining randomness and probability in infinite versus finite contexts, emphasizing that while an event with zero probability can still occur, it is highly unlikely. The conversation also touches on the concept of measure theory, which explains how probabilities behave in infinite sets. Overall, the intricacies of probability in infinite series reveal significant philosophical and mathematical implications.
  • #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.
 
Physics news on Phys.org
  • #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).
 

Similar threads

Replies
29
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
1
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 0 ·
Replies
0
Views
2K