Scientific method / Experimental design / Dedicated lab room

Three glass vessels with different blue liquid levels and matching samples illustrate changing one condition and measuring an outcome. — Choose one independent variable, define the outcome you will measure, and repeat the setup so the results can be compared.

← RETURN TO LESSONLAB DOSSIER / GUIDED VIDEOENGLISH VOICEOVER · CAPTIONS

SCIENTIFIC METHOD · GRADES 4–8

Plan a fair seed experiment

INVESTIGATION QUESTIONHow many controls and repeats make this test clearer?

● ILLUSTRATIVE SCIENCE MODEL

ENGLISH CAPTIONS

Ask how daily light affects mean bean height over two weeks.

0.0 / 3.0 s

01 / SCIENCE

What explains the result?

Replicates reveal natural variation and make a group average less dependent on one unusual seedling.

02 / EVERYDAY CONNECTION

Where does this matter?

Experimental design helps researchers choose samples and controls before collecting costly data.

03 / MODEL LIMIT

What should you keep in mind?

More replicates improve reliability but do not fix biased selection or uncontrolled conditions.

Continue to the interactive experiment ↓

Two matched laboratory setups show identical equipment and samples, with only the light condition changed. — The paired setups keep sample, vessel, timing, and measurement equipment the same while one condition changes.

YOUR TASK

How many controls and repeats make this test clearer?

Plan a fair seed experiment: experiment-specific laboratory scene

READ THE BENCH CARD

Build a fair and repeatable comparison

Choose one factor, a measurable response, and controls before accepting the study plan. More replicates improve reliability but do not fix biased selection or uncontrolled conditions.

MATERIALS / DATASeedlings · Three light settings · Data sheet

MISSION · TEST LIGHT AND BEAN GROWTHBuild a fair comparison with one planned change and an observable outcome.

Keep seed variety, pot size, soil and watering matched; repeat each condition.

Change

Measure

Include fair-test controls

Same bean varietySame water amountAt least three plants per condition

WHAT TO TAKE AWAY

Replicates reveal natural variation and make a group average less dependent on one unusual seedling.

WHERE THIS IS USED

Experimental design helps researchers choose samples and controls before collecting costly data.

MODEL LIMIT More replicates improve reliability but do not fix biased selection or uncontrolled conditions. The activities on this page do not store classroom measurements.

A laboratory notebook, measuring instruments, repeated sample readings, and a graph show how observations become evidence. — Write down each trial before interpreting the pattern. Repeated measurements help show variation instead of hiding it.