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Scatter diagrams and correlation

3 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What does correlation tell you, and why does it not prove causation?

Vocabulary of correlation (positive, negative, zero, causation, association, interpolation, extrapolation); describing correlation by inspection as strong or weak; correlation does not imply causation; spurious correlation.
A focused answer to Edexcel GCSE Statistics on correlation, covering the vocabulary of correlation, describing correlation by inspection as strong or weak and positive or negative, why correlation does not imply causation, spurious correlation, and interpolation versus extrapolation.
9 min answer →

How do you fit a line to data and use it to make and interpret predictions?

Line of best fit by eye through the double mean point; the regression line y = a + bx; interpreting gradient and intercept; using the line for prediction with awareness of interpolation and extrapolation.
A focused answer to Edexcel GCSE Statistics on lines of best fit and regression, covering drawing a line of best fit through the double mean point, the regression line y = a + bx, interpreting the gradient and intercept, and using the line to make predictions with awareness of extrapolation.
9 min answer →

How do Spearman's rank and the PMCC measure correlation, and how do they differ?

Calculating and interpreting Spearman's rank correlation coefficient; interpreting Pearson's product moment correlation coefficient; the distinction between rank correlation and product moment correlation.
A focused answer to Edexcel GCSE Statistics (Higher tier) on correlation coefficients, covering calculating and interpreting Spearman's rank correlation coefficient, interpreting Pearson's product moment correlation coefficient, and the distinction between rank correlation and linear product moment correlation.
10 min answer →