Solution — 2021 Question 9 Regression

Using GC, $$r=-0.966∎$$

This indicates a strong negative linear correlation between the age of an adult male and their maximum walking speed. In context, this means that older adult males tend to have lower maximum walking speeds.

Using GC, the equation of the regression line of $y$ on $x$ is $$y=-0.00893x+2.61∎$$

When $x=55,$

Hence the maximum walking speed is estimated to be $2.12∎{\text{ ms}}^{-1}$

This estimate is reliable because $x=55$ lies within the range of the data $19\le x\le 73$ and $r=-0.96606\approx -1$ which indicates a strong negative linear correlation between $x$ and $y∎$