Population

A population is the entire group you actually want to learn about — every person, item, or event that your question is really about. It is defined by your question, not by what data happens to be easy to collect.

If you ask “what fraction of adults in Taiwan own a car,” the population is all adults in Taiwan, even if you can only realistically reach a few thousand of them. Naming the population precisely is the most underrated step in any study: vague populations (“users,” “customers”) lead to conclusions that quietly apply to a narrower or different group than you think.