Fair Tests and Controlled Variables

Lab Brief #3

🎯 Your mission

Run the experiment. Find out what really happens.

⚡ The twist

Nature loves to surprise the careful watcher.

What you'll learn

A fair test changes one thing at a time and holds everything else steady. If you change the ramp angle and the ball at once, a difference in distance tells you nothing about which change caused it.

Key words

fair test
An investigation in which only one variable is changed at a time.
controlled variable
A factor deliberately held constant so it cannot affect the outcome.

Make a hypothesis first

Before you start: write down what you think will happen, and why.

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

ramp
ball
metre rule
notebook

⚠️ Safety first

Clear the run-out area so nobody trips on a rolling ball.

Step 1 of 4 · Read

Think about what you just learned: say what "fair test" and "controlled variable" mean in your own words before you start.

Step 2 of 4 · Do

Roll the same ball down a ramp at three angles, keeping release point, surface and ball identical. Record distance travelled three times per angle, then deliberately change two things at once and show why that run is uninterpretable.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

In a fair test you change:

How sure are you?😐 maybe

Question 2 of 2

Holding the ball type constant while changing ramp angle makes ball type a:

How sure are you?😐 maybe

Mind = blown

🔬 The more you look, the more nature shows you.

Nice work!

You got 0 of 2 right.

Next: Choosing the Right Graph All lessons

🎯

Next Smart Experiment

We'll pick an experiment that matches exactly how you're thinking right now.

✨ More to explore

🌍 Where you see this in real life: This shows up in your everyday life more than you'd think.

🏆 Stretch challenge (try it this week): Try one experiment in real life this week — even a tiny one.

👨‍👩‍👧 For the dinner table: “What's the most surprising thing you learned today?”

📊Share card

Share this experiment

Send it to a parent who's looking for a 10-minute kitchen science win.

Fair Tests and Controlled Variables

Next Smart Experiment

Share this experiment

Fair Tests and Controlled Variables

Done with science? Try something else

Your Cart (0)