The city of Toronto wants to understand how people commute to make informed policy decisions about transportation in the city.

First, the government needs to understand which group of people they are interested in. Certainly, the group is smaller than all of the people in the Canada. However, it is also too confined to only study people living in Toronto, as people commuting into the city contribute to daily traffic patterns.

Once the city determines their population of interest, they realize it is infeasible to track the transportation of the entire population, so they decide to study a sample, or subset of the population, to make predictions about the population.