Probability and population proportion

When sampling from any population, whether finite or infinite,

The probability of sampling any value or range of values equals the proportion of these values in the population.

Probability and long-term proportion

An alternative but equivalent way to think about probability arises when we can imagine repeatedly selecting more and more values from the population (e.g. repeating an experiment). The probability of any value or range of values is the limiting proportion of these values as the sample size increases.

The equivalence of the two definitions is called the law of large numbers.