Year 9 Science · Unit 4 · Lesson 14
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Learning Goals
True or False? Fix the false ones
Circle T or F for each statement. If the statement is false, rewrite it correctly on the line below.
A correlation between two variables proves that one causes the other.
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A confounding variable is a hidden third factor that can drive two other variables at once.
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A very large sample size turns any correlation into proof of cause.
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A controlled experiment, changing one variable while keeping others the same, is the strongest test for cause.
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Scenario
A newspaper reports that students who own more books at home also get higher test scores. The headline reads: "Buying books makes children smarter!" A reader, Sam, wants to know whether the headline is fair.
(a) Is the relationship between number of books and test scores a correlation or a proven causation? Explain how you know.
(b) Suggest a confounding variable that could explain why both numbers rise together, without books being the cause.
(c) Describe one controlled experiment scientists could run to test whether owning more books really causes higher test scores.
1. A study of 100,000 people finds that towns with more firefighters have more fire damage. Explain why this does not mean firefighters cause fire damage, and name the confounding variable.
2. A wellness video claims "celery juice cures anxiety" because many viewers who drink it report feeling calmer. Explain why this is only a correlation, and describe how a large dataset and statistics could help validate the finding.
Wrap Up
In one sentence, what was the main idea of this lesson?