I have an (intuitive) understanding of what a random variable and a sample are. However, I am not sure how a random variable is related to a sample.
Suppose we have a population of people. Sampling from that population means to take a subset (which we call "sample") of those people.
What can be considered a random variable while sampling, once we have a sample and when we take an element from this sample? How many random variables are involved in the process of sampling or once we have the sample?
I would appreciate seeing many real-world examples of the sampling process where you explain which and how many random variables are involved.
1. This question is different from What is the difference between random variable and random sample?.
2. Please, avoid defining what a random variable and sample are. I already know what they are and, if I forget the definitions, I can look them up again!