Population (statistics) facts for kids

In statistics, a population is a complete group of things that you are interested in studying. Imagine you want to learn something about a specific group, like all the students in your school, or all the trees in a certain park. This entire group is your population.

When we study a population, we often take a small group from it, called a sample. By studying this sample, we can make smart guesses or draw conclusions about the entire population. For example, if you want to know the average height of all students in your school, it would be hard to measure everyone. Instead, you could measure a smaller group (a sample) and use that information to estimate the average height of all students. To make sure your guess is accurate, the sample needs to be chosen randomly.

What is a Statistical Population?

A statistical population is the whole group of items or individuals that a study is about. It's not just about people; it can be anything! For instance, if you're studying crows, your population might be all the crows living in your town. Sometimes, the population might be limited by things like geography (only crows in a certain county) or time (only crows alive right now).

Why Do We Study Populations?

We study populations to understand their characteristics. Instead of looking at every single item in a huge group, we often use a smaller, carefully chosen group called a sample. This helps us make inferences (smart guesses) or estimates about the whole population. For example, if we want to know the average weight of all adult crows in a specific area, we can't weigh every single one. So, we take a sample.

Real-World Examples of Populations

A population can be thought of in two main ways: as a group of actual things, or as a group of measurements.

Population of Things

This is the most common idea of a population. It's a collection of actual items, people, animals, or events.

• Example: All the students in a particular grade level.
• Example: Every single car produced by a certain factory in a year.
• Example: All the trees in a specific forest.

Population of Measurements

Sometimes, the population refers to a set of values or measurements, not just the physical items themselves.

• Example: If we are interested in the weight of all adult crows in Cambridgeshire, the population of "things" is all those crows. But the population of "measurements" would be the list of all their individual weights.
• Example: The scores of all students on a math test.
• Example: The daily temperature readings for a city over a year.

Why Are Random Samples Important?

To make sure our guesses about a population are fair and accurate, the sample we choose must be random. A random sample means that every item or individual in the population has an equal chance of being chosen for the sample. If a sample isn't random, it might not truly represent the whole population, and our conclusions could be wrong. For example, if you only ask your friends about their favorite ice cream flavor, that's not a random sample of all kids in your town. Your friends might have similar tastes!

See also

In Spanish: Población estadística para niños