2026 NCHS P1 Q21

The stem-and-leaf diagram below shows the times taken, in minutes, for 10 boys from school ABC to complete a 400 m swim.

Key: \(7\mid4\) represents 7.4 minutes.

1. Calculate an estimate for
   1. the mean swim time,[1]
   2. the standard deviation of the swim time.[1]
2. Another group of 10 boys from school XYZ have a mean swim time of 8.3 minutes and a standard deviation of 0.97 minutes in the 400 m swim. Make two comments comparing the mean and distribution of the swim time of the 20 boys from both schools.[2]