# Does $X$ (a random variable) usually refer to the population or the sample? [duplicate]

Like the title says, does $X$ (a random variable) usually refer to the population or the sample?

A random variable, by definition, is a misurable function. If you estract a sample from a population, they follow the same distribution, so the random variable can describe both. When you use the term "Random Variable" you refer to a function from a set to another, the first being called "sample space" and the second $\mathbb{R}^n$.