Pearson Correlation Coefficient
The product moment correlation coefficient (PMCC) calculated as r = Σ(x - x̄)(y - ȳ) / √[Σ(x - x̄)² × Σ(y - ȳ)²], ranging from -1 to +1.
Real World
An economist calculates PMCC between UK household income and supermarket spend data from the ONS, finding r = 0.87 — strong evidence of a positive linear relationship.
Exam Focus
Quote the PMCC value to 3 significant figures and interpret sign and magnitude explicitly — 'strong positive linear correlation' earns interpretation marks.
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