01 / Start with a question.
A student tests whether light changes plant growth. They have 12 similar seedlings and split them equally into a bright group and a shaded group. How many seedlings are in each group?
02 / Explain the why.
Six seedlings belong in each group. But a fair test requires more than equal numbers: keep water, soil, temperature and observation time consistent. What could you conclude if both groups grow by the same amount?
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03 / Keep asking.
What assumption did you make? How could you test it? Can you describe your reasoning to someone who has never seen this question?
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