Controlling variables
Plan different types of scientific enquiries to answer questions, recognising and controlling variables where necessary
What a learner can do afterwards
- Independently plan an investigation identifying the independent, dependent, and controlled variables
- Choose the appropriate type of enquiry for the question (fair test, observation over time, pattern seeking, research)
- Explain why controlling variables is essential for valid results
The lesson
You already know how to run a fair test: change one thing, keep everything else the same. Scientists have names for these parts. The independent variable is the one thing you change on purpose. The dependent variable is what you measure to see what happened. The controlled variables are everything else you keep exactly the same.
Zara wants to know if more water makes bean plants grow taller. She changes the amount of water each plant gets. That is her independent variable. She measures each plant's height after two weeks. That is her dependent variable. She keeps the pot size, the sunlight, and the seed type the same for every plant. Those are her controlled variables.
A fair test is not the only kind of scientific enquiry. Watching something change over days or weeks, like the weather, is called observation over time. Comparing many different things to look for a link, like whether taller people have bigger feet, is called pattern seeking. If the answer is already written down somewhere, you can find it through research instead of running an experiment.
Repeating your test and keeping the controlled variables the same is what makes your results trustworthy. If you changed two things at once, you would never know which one caused the difference.
One thing you change, one thing you measure, everything else kept the same, then repeat to be sure.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.