(i) To find the mean:

\(\bar{x} = \frac{\Sigma x}{n} = \frac{745}{18} = 41.4\)

To find the standard deviation:

\(s = \sqrt{\frac{\Sigma x^2}{n} - \left(\frac{\Sigma x}{n}\right)^2} = \sqrt{\frac{33951}{18} - \left(\frac{745}{18}\right)^2} = 13.2\)

(ii) Let the age of the person who left be \(x\).

The sum of the ages of the remaining 17 people is:

\(17 \times 41 = 697\)

Therefore, \(745 - x = 697\), giving \(x = 48\).

To find the standard deviation of the remaining 17 people:

\(s = \sqrt{\frac{\Sigma x^2 - x^2}{17} - (41)^2} = \sqrt{\frac{33951 - 48^2}{17} - 41^2} = 13.4\)