9231 P23 - Jun 2017 - Q8 - 9 marks
6159
The number, \(x\), of beech trees was counted in each of 50 randomly chosen regions of equal size in beech forests in country \(A\). The number, \(y\), of beech trees was counted in each of 40 randomly chosen regions of the same equal size in beech forests in country \(B\). The results are summarised as follows.
\[\Sigma x=1416 \quad \Sigma x^{2}=41100 \quad \Sigma y=888 \quad \Sigma y^{2}=20140\]
Find a 95\% confidence interval for the difference between the mean number of beech trees in regions of this size in country \(A\) and in country \(B\).
