Edexcel IAL S1 Correlation and Regression Questions
Product-moment correlation coefficient (PMCC), scatterplots, least-squares regression line y on x.
- S1 · Statistics 1
- Calculator allowed
- 35 practice questions
What the questions test
The 35 S1 correlation and regression practice questions cover:
Worked example 1
A dataset of 20 observations produced the following summary statistics: $\sum x = 140$, $\sum y = 200$, $\sum x^2 = 1250$, $\sum y^2 = 2600$, and $\sum xy = 1100$. Calculate the product moment correlation coefficient.
Mark scheme
- M1 for calculating $S_{xx} = 1250 - \frac{140^2}{20} = 270$ and $S_{yy} = 2600 - \frac{200^2}{20} = 600$.
- M1 for calculating $S_{xy} = 1100 - \frac{140 \times 200}{20} = -300$.
- M1 for setting up the PMCC calculation $r = \frac{-300}{\sqrt{270 \times 600}}$.
- A1 for evaluating the final correlation coefficient as $r \approx -0.745$ (to 3 s.f.).
Worked example 2
Using the summary statistics $\sum x = 140$, $\sum y = 200$, $S_{xx} = 270$, $S_{xy} = -300$, and $n=20$, find the equation of the regression line of $y$ on $x$ in the form $y = a + bx$.
Mark scheme
- M1 for calculating the gradient $b = \frac{S_{xy}}{S_{xx}} = \frac{-300}{270}$.
- A1 for $b = -\frac{10}{9}$ or $\approx -1.11$.
- M1 for calculating the means $\bar{x} = 7$, $\bar{y} = 10$, and determining the intercept $a = 10 - (-\frac{10}{9})(7)$.
- A1 for final equation $y = 17.8 - 1.11x$ (or $y = \frac{160}{9} - \frac{10}{9}x$).
FAQ
What correlation and regression is in Edexcel IAL S1?
Product-moment correlation coefficient (PMCC), scatterplots, least-squares regression line y on x.
Is S1 a calculator paper?
Yes, a calculator is allowed in S1, but method marks are only given for working you write down.
How are S1 correlation and regression questions marked?
With M marks for a correct method, A marks for accurate answers that depend on the M mark before them, and B marks for independent results, as in the worked examples on this page.