--- title: "Controlling variables" description: "Plan different types of scientific enquiries to answer questions, recognising and controlling variables where necessary" canonical: https://lightmysky.com/learn/science/controlling-variables-mt_ArVBEpMAPk source: https://lightmysky.com/learn/science/controlling-variables-mt_ArVBEpMAPk.md retrieved: 2026-10-19 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Controlling variables Plan different types of scientific enquiries to answer questions, recognising and controlling variables where necessary Subject: Science · Area: Scientific Inquiry · Ages 9 to 11 Page: https://lightmysky.com/learn/science/controlling-variables-mt_ArVBEpMAPk ## Ready when they can - 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 ## Lesson: Controlling variables 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. **Example.** 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. *(drawing: Follow these steps in order every time you plan an investigation.)* **Tip.** 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. **Recap.** One thing you change, one thing you measure, everything else kept the same, then repeat to be sure. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Using evidence to answer questions](https://lightmysky.com/learn/science/using-evidence-to-answer-questions-mt_CVywzrjT_c) - [Choosing a strategy](https://lightmysky.com/learn/learning-to-learn/choosing-a-strategy-mt_q7zxOloj_L) - [Fair testing](https://lightmysky.com/learn/science/fair-testing-mt_qgb76wHN2X) - [Planning a task](https://lightmysky.com/learn/learning-to-learn/planning-a-task-mt_QR3vxbN1o4) - [Asking scientific questions](https://lightmysky.com/learn/science/asking-scientific-questions-mt_XirhnAB6Ye) ## Opens up - [Fair testing (age 9+)](https://lightmysky.com/learn/science/fair-testing-age-9-mt_5PgQB0QkWi) - [Controlling variables (age 11+)](https://lightmysky.com/learn/science/controlling-variables-age-11-mt_Ae56umVlTT) - [Fair testing (age 8+)](https://lightmysky.com/learn/science/fair-testing-age-8-mt_eoPcc4nrBE)