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Paradoxes of Probability and Other Statistical Strangeness

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Re: Paradoxes of Probability and Other Statistical Strangeness

#4

Another "paradox": even though it's possible to randomly pick a rational number from the reals, the probability of this happening is 0.

Please describe how it is possible to pick such a number. For example, I can readily imagine how to pick a random 32b float, but that it is an entirely problem with a nonzero probability.

Re: Paradoxes of Probability and Other Statistical Strangeness

#5
post #4

Another "paradox": even though it's possible to randomly pick a rational number from the reals, the probability of this happening is 0.

Please describe how it is possible to pick such a number. For example, I can readily imagine how to pick a random 32b float, but that it is an entirely problem with a nonzero probability.

*entirely different

Re: Paradoxes of Probability and Other Statistical Strangeness

#6
post #4

Another "paradox": even though it's possible to randomly pick a rational number from the reals, the probability of this happening is 0.

Please describe how it is possible to pick such a number. For example, I can readily imagine how to pick a random 32b float, but that it is an entirely problem with a nonzero probability.

Usually in math we assume the axiom of choice :) https://en.wikipedia.org/wiki/Axiom_of_choice I'm assuming this could somehow lead to such a "random" pick in the technical sense.

In terms of implementation, I'm not aware of an algorithm that can randomly pick a real number on an actual computer. Perhaps a mathematician could show how to pick one on some abstract machine with infinite resources, and not constrained by finite bit representations of numbers.

Re: Paradoxes of Probability and Other Statistical Strangeness

#7
post #4

Another "paradox": even though it's possible to randomly pick a rational number from the reals, the probability of this happening is 0.

Please describe how it is possible to pick such a number. For example, I can readily imagine how to pick a random 32b float, but that it is an entirely problem with a nonzero probability.

In probability theory, when dealing with continuous sample spaces / random variables, events with probability 0 still have a chance of occurring, and events with probability 1 stil l have a chance of NOT occurring, see:

https://en.wikipedia.org/wiki/Almost_surely

This strange property comes from strange properties of the real numbers (and uncountably infinite sets) that give rise to things like:

https://en.wikipedia.org/wiki/Banach%E2%80%93Tarski_paradox

Measure theory deals with resolving this:

https://en.wikipedia.org/wiki/Measure_(mathematics)

Re: Paradoxes of Probability and Other Statistical Strangeness

#9

Another "paradox": even though it's possible to randomly pick a rational number from the reals, the probability of this happening is 0.

There is no uniform probability distribution on the reals.

Perhaps you meant the interval from 0 to 1?

Re: Paradoxes of Probability and Other Statistical Strangeness

#10

Another "paradox": even though it's possible to randomly pick a rational number from the reals, the probability of this happening is 0.

there are a number of similar paradoxes that arise when considering infinities of different sizes!

Infinity Paradoxes - Numberphile - https://www.youtube.com/watch?v=dDl7g_2x74Q

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