The scatterplot below shows the rainfall (in mm) and the percentage of clear days for each month of 2023.
An equation of the line of best fit for this data set is
\(\textit{rainfall}\ = 131-2.68 \times\ \textit{percentage of clear days} \)
- Using coordinates at the graph extremities or otherwise, draw this line on the scatterplot. (2 marks)
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- Describe this association in terms of strength and direction. (1 mark)
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i.
ii. \(\text{Strength: moderate (data points are moderately close to the LOBF)}\)
\(\text{Direction: negative (as percentage of clear days ↑, rainfall ↓)}\)
i. \(\text{Calculate values at the limits of the graph:}\)
\((0, 131)\ \ \Rightarrow \ \ y \text{-intercept}\ = 131 \)
\( (30, 50.6)\ \ \Rightarrow \ \text{At}\ x=30, \ y=131-2.68 \times 30 = 50.6 \)
ii. \(\text{Strength: moderate (data points are moderately close to the LOBF)}\)
\(\text{Direction: negative (as percentage of clear days ↑, rainfall ↓)}\)