What is a Class Interval? - Definition & Example

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: How to Find a Class Interval

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:04 What Is a Class Interval?
  • 1:33 An Example Using Class…
  • 3:21 Lesson Summary
Add to Add to Add to

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Login or Sign up


Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Jenny Homer

Jenny has masters' degrees in public health and public administration.

This lesson introduces class intervals, a way to divide data into groups. Learn when to use class intervals and how they can be helpful, using the interesting example of the U.S. Census.

What Is a Class Interval?

Ever wonder exactly how many people live in your state? Or in the whole country? The United States government takes a census, or a count of the number of people living in the country. In 2010, the population of the United States was 308.7 million people. Taking a census is such a big job that it's done only once every ten years.

The U.S. Census also collects information about people, like how old they are and how long they have gone to school. The census is collecting data, numbers that give information.

Think about the question, 'How old are you?' There are a lot of different answers you could give, from 1 if you're a very little kid all the way past 100 if you're very old. But knowing exactly how many 1-year-old kids, how many 2-year-old kids, how many 3-year-old kids, and so on is not always the easiest or best way to look at the data. That is where it's helpful to use a class interval. A class interval is a way to divide data and group certain answers together.

When determining the class interval to use with your data, you must follow three rules:

  1. The same person or unit can be in only one class interval.
  2. The width or range of numbers in the class intervals must be equal.
  3. There are no numbers left out of the groupings.

And, although not a rule, you typically want to have 10 to 20 class intervals.

An Example Using Class Intervals

Let's find out what this means for the U.S. Census. Individually listing the number of 1-year-old kids, 2-year-old kids, 3-year-old kids, and so on, could be too much. It would make more sense to group the ages into class intervals.

Do class intervals work here? Let's look at our rules:

Rule #1 says the same person or unit can be in only one class interval. Can a person be 1 and 10 years old at the same time? Of course not! You can only be one age at a time, so the same person can only be in one class interval at a time.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create An Account