A-Level Further Maths · Further Statistics
Chi-Squared Tests
What is it
A chi-squared test compares observed data against expected data to test whether a difference is statistically significant or simply due to random chance, commonly used to test for independence or goodness of fit.
Why it matters
Chi-squared tests are one of the most widely used statistical tools in real research — testing whether a survey result reflects a genuine pattern or is just noise is exactly the kind of question this test answers.
Exam tip
Always check that expected frequencies are large enough (typically at least 5) before running a chi-squared test — the test becomes unreliable with small expected frequencies, and exam questions often test whether you check this assumption.
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