Fair Tests to Improve a Design
Aligned to 3-5-ETS1-3 — Next Generation Science Standards.
What this lesson teaches
A fair test changes only one thing at a time so you know what made the difference. Fair tests help you find which part of a design to fix.
Worked examples
Example 1
To make a paper airplane fly farther, you throw it the same way each time and only change the wing folds.
Example 2
To find the best plant food, give every plant the same pot, soil, light and water — and change only the food.
Example 3
If you change two things at once and the result improves, you will not know which change did it. That is why fair tests change one variable.
Practice questions
- Build a simple model, like a paper boat, and decide one thing you will change.
- Test it while keeping everything else the same, and measure the result each time.
- Explain which change worked best and what you would improve next.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Pruebas justas para mejorar un diseño
Una prueba justa cambia solo una cosa a la vez para que sepas qué hizo la diferencia. Las pruebas justas te ayudan a encontrar qué parte de un diseño arreglar.
Ejemplo 1: Para que un avión de papel vuele más lejos, lo lanzas de la misma manera cada vez y solo cambias los dobleces de las alas.
Ejemplo 2: Para hallar el mejor abono, dale a cada planta la misma maceta, tierra, luz y agua — y cambia solo el abono.
Ejemplo 3: Si cambias dos cosas a la vez y el resultado mejora, no sabrás cuál cambio lo logró. Por eso las pruebas justas cambian una sola variable.
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