(a)[4]
Produce a back-to-back stem-and-leaf diagram for the data, placing the Gulls on the left-hand side.
(b)[3]
Determine the median and the interquartile range of the times of the runners from the Gulls.
(c)[2]
Two further teams of runners, the Eagles and the Swifts, also competed in the event. The times recorded in seconds for 20 runners from the Eagles and 30 runners from the Swifts are represented by $x$ and $y$ respectively. It is given that $\sum x = 175.0$ and that the mean of $y$ is $8.4$. Find the mean of the times taken by all 50 runners.
(d)[3]
It is stated that $\sum x^2 = 1823.0$. It is also stated that the standard deviation of the times taken by all 50 runners is $1.38$ seconds. Find the value of $\sum y^2$, correct to 1 decimal place.