> > For a simple starter example, we know that every person on Earth has a height, defined as the distance from the bottom of their feet to the top of their hea

> > For a simple starter example, we know that every person on Earth has a height, defined as the distance from the bottom of their feet to the top of their head when standing upright. > This is a silly mistake to make in an article on statistics. Any statistician worth their salt can see the problem with an operational definition of height that starts with "bottom of their feet". You missed the forest for the trees. > Why would we select a subset at random? Why shouldn't we try to select a representative subset? We know from experience that biological sex, country of birth, and affluence of family are three strong predictors of height. Why shouldn't we deliberately select a subset that balances out these variables in proportion to their population? Random subsets are core to statistics, and they are independent of representative samples. You choose random subsets so that you can compute statistics with well defined confidence intervals (as in the less randomness there is in your sample the poorer/hard to quantify your confidence would be). You use representative samples when you want to compare groups. Representative samples should still be random per group.