By understanding calculus, people can use math to make predictions about things that change over time. We use estimation regularly to determine such things as how many, how heavy, and how full. Being a good estimator also helps children know if answers on calculators or other computer generated data make sense. Measurement is determining the lengths, areas, volume, time, and other quantities. Children need to know common units of measure such as inches or kilograms and how to use measurement tools.
Statistics is the collection and analysis of numerical data.
Taking a census and counting people is a statistical activity.