Calling the entire roll is a census, asking just a few is sampling; the sample size is written n, and the bigger it is the closer to the truth
Module goal. Build the habit of answering questions with data, understand where data comes from and how to sample without bias, laying the raw-material foundation for everything that follows
eastmath.com · 34.1 Starting with Data: Collecting and Sampling · 34.1.3 Census and Sampling