A meteorologist recorded the average daily rainfall (RRR) and the number of umbrellas sold (UUU) at a local shop for 12 selected days.
| Rainfall (R R\,R mm) | 2.5 | 4.0 | 5.5 | 8.0 | 10.5 | 12.0 | 15.0 | 18.0 | 20.0 | 22.0 | 25.0 | 28.0 |
| Umbrellas sold (UUU) | 3 | 7 | 5 | 12 | 10 | 18 | 15 | 22 | 19 | 28 | 24 | 30 |
Draw a scatter graph for this information.
Give an interpretation of the correlation between rainfall and umbrellas sold.
The equation of the regression line is U=1.05R+1.22U = 1.05R + 1.22U=1.05R+1.22.
Give an interpretation of the gradient of this regression line.
The product moment correlation coefficient is calculated to be 0.55.
Stating your hypotheses clearly, test at the 5% significance level whether there is a positive correlation between rainfall and umbrella sales.
Determine whether you would reach the same conclusion at the 1% significance level.
202 exam-style questions on Edexcel A Level Maths Regression, Correlation and Hypothesis Testing, covering 1.1 Exponential Models, 1.2 Measuring Correlation, and 1.3 Hypothesis Testing for Zero Correlation. Each one has a worked solution and a mark scheme showing where the marks go.