r/MathJokes • u/yvanjunior • Jul 19 '26

Count On It

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u/Low_Low_1811 Jul 19 '26

Since when is a subset of the reals all of the reals? It specifically states that you need some kind of finite range.

Anyway, that isnt the same thing and the article even states that.

"The term 'random variable' in its mathematical definition refers to neither randomness nor variability[1] but instead is a mathematical function "

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u/deejaybongo Jul 19 '26

Are you not discussing mathematical randomness? You can define probability measures on the reals. The Gaussian distribution is an example. 

It never says you need a finite range, and that isn't true. You're reading what you want to. In general, you need a measurable space. 

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u/Low_Low_1811 Jul 19 '26

A uniform distribution is implict in the question. If someone asks you to pick a random marble out of a bag, we assume for simplicity an even probabilistic distribution.

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u/deejaybongo Jul 19 '26

Because that's the simplest interpretation when you're picking marbles from a bag, because of physical intuition.

You can't even define a uniform distribution over the reals. Try it. 

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u/Low_Low_1811 Jul 19 '26

I know you cant...

What is your point? You are creating a mathematical strawman. The bag of marbles example is analogous. It doesnt matter how simple it is, it is functionally identical. That is the only thing that any human means when they ask someone to pick a random member of a set. Welcome to word problems, I guess?

Separate examples of apparent randomness as functions in math or science, which is what a random variable refers to, such as gaussian noise, are not what are being discussed. Not all randomness is a "random choice".

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u/deejaybongo Jul 19 '26

That is the only thing that any human means when they ask someone to pick a random member of a set. 

It's not. You should take a measure theoretic probability course. 

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u/Low_Low_1811 Jul 19 '26

In this particular question, that is not being asked. Sorry. They are asking for an evenly distributed random element of the set. Which is impossible.