2.2 What is a Sample?

We almost never have full access to the population distribution that we care about, so we have to settle for a sample.

• consists of some number n of “individuals” from the population
  • poll 2000 likely voters
  • randomly select 50 trees from the forest to measure
  • roll the dice 100 times
• drawn at random from the population
• represented by a distribution over the same variables as the population

Whatever statistic we wanted to calculate for the population, we instead calculate for the sample.