What is a Null Hypothesis? - Definition & Examples

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Descriptive Research Design: Definition, Examples & Types

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

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:00 What Is a Null Hypothesis?
  • 1:08 What Is an Alternative…
  • 1:55 Examples
  • 3:01 Lesson Summary
Save Save Save

Want to watch this again later?

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

Log in or Sign up

Speed Speed Audio mode

Recommended Lessons and Courses for You

Lesson Transcript
Karin Gonzalez

Karin has taught middle and high school Health and has a master's degree in social work.

Expert Contributor
Robert Ferdinand

Robert Ferdinand has taught university-level mathematics, statistics and computer science from freshmen to senior level. Robert has a PhD in Applied Mathematics.

This lesson will give the definition of a null hypothesis, as well as an alternative hypothesis. Examples will be given to clearly illustrate the concept of a null hypothesis versus an alternative hypothesis.

What Is a Null Hypothesis?

A hypothesis is a speculation or theory based on insufficient evidence that lends itself to further testing and experimentation. With further testing, a hypothesis can usually be proven true or false. Let's look at an example. Little Susie speculates, or hypothesizes, that the flowers she waters with club soda will grow faster than flowers she waters with plain water. She waters each plant daily for a month (experiment) and proves her hypothesis true!

A null hypothesis is a hypothesis that says there is no statistical significance between the two variables in the hypothesis. It is the hypothesis that the researcher is trying to disprove. In the example, Susie's null hypothesis would be something like this: There is no statistically significant relationship between the type of water I feed the flowers and growth of the flowers. A researcher is challenged by the null hypothesis and usually wants to disprove it, to demonstrate that there is a statistically-significant relationship between the two variables in the hypothesis.

What Is an Alternative Hypothesis?

An alternative hypothesis simply is the inverse, or opposite, of the null hypothesis. So, if we continue with the above example, the alternative hypothesis would be that there IS indeed a statistically-significant relationship between what type of water the flower plant is fed and growth. More specifically, here would be the null and alternative hypotheses for Susie's study:

Null: If one plant is fed club soda for one month and another plant is fed plain water, there will be no difference in growth between the two plants.

Alternative: If one plant is fed club soda for one month and another plant is fed plain water, the plant that is fed club soda will grow better than the plant that is fed plain water.


Example 1:

Null Hypothesis: The Earth is flat.

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

Additional Activities

Null Hypothesis: Questions for Additional Practice

1. The average life of a car battery of a certain brand is five years. This information is gathered using data obtained from people who have purchased and used this brand of battery over a period of several years. A researcher at the battery company develops a new type of car battery and claims that the average life of this battery is more than five years. To determine whether this claim is true, one would need to do some hypothesis testing. What would be the null hypothesis and the alternative hypothesis for this hypothesis test?

2. Past research data from a period of over several years states that the average life expectancy of whales is 100 years. A researcher at a laboratory wishes to test this hypothesis. To that end they procure a sample of life spans of several whales. What is the null hypothesis and the alternative hypothesis that this researcher will establish?


1. The researcher's null hypothesis will be: ''The average life of the new car battery is five years.''

Then their alternative hypothesis will read: ''The average life of the new car batter is more than five years.''

2. The null hypothesis for the researcher will state that, ''The average life expectancy of whales is exactly equal to 100 years.''

Their alternative hypothesis will read: ''The average life expectancy of whales is not equal to 100 years.''

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 200 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