Testing Fairly
Aligned to 3-5-ETS1-3 — Next Generation Science Standards.
What this lesson teaches
To find out which design works best, engineers run a fair test. A fair test changes only one thing at a time and keeps everything else the same, so the results can be trusted. Watching where a design fails shows what to improve.
Worked examples
Example 1
To see which paper airplane flies farther, you throw both with the same force from the same spot, changing only the plane's shape — not how hard you throw.
Example 2
To test which cup keeps water hottest, start with the same amount of water at the same temperature in the same room.
Example 3
Repeat the test. One trial can be a fluke; three trials that agree is evidence.
Practice questions
- In a race between two toy cars, what should you keep the same to make the test fair?
- Plan a fair test to find out which cup keeps water warm the longest.
- Explain why changing only one thing at a time makes a test fair, and how a failure can help you improve a design.
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
Probar de manera justa
Para descubrir qué diseño funciona mejor, los ingenieros hacen una prueba justa. Una prueba justa cambia solo una cosa a la vez y mantiene todo lo demás igual, para que se pueda confiar en los resultados. Observar dónde falla un diseño muestra qué mejorar.
Ejemplo 1: Para ver cuál avión de papel vuela más lejos, lanzas los dos con la misma fuerza desde el mismo lugar, cambiando solo la forma del avión — no la fuerza con que lo lanzas.
Ejemplo 2: Para probar qué vaso mantiene el agua más caliente, empieza con la misma cantidad de agua a la misma temperatura en el mismo cuarto.
Ejemplo 3: Repite la prueba. Un solo intento puede ser suerte; tres intentos que coinciden son evidencia.
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