(i) To calculate the mean, use the midpoints of each class interval:

Midpoints: 3, 8, 15.5, 25.5, 40.5

Mean = \(\frac{(3 \times 59) + (8 \times 67) + (15.5 \times 38) + (25.5 \times 18) + (40.5 \times 11)}{193} = 11.4\)

To calculate the standard deviation, use:

\(\sigma^2 = \frac{(3^2 \times 59) + (8^2 \times 67) + (15.5^2 \times 38) + (25.5^2 \times 18) + (40.5^2 \times 11)}{193} - (11.4)^2\)

\(\sigma = 9.78 \text{ or } 9.79\)

(ii) For the histogram, calculate frequency densities:

Frequency density = \(\frac{\text{Frequency}}{\text{Class width}}\)

Class widths: 5, 5, 10, 10, 20

Frequency densities: \(\frac{59}{5} = 11.8, \frac{67}{5} = 13.4, \frac{38}{10} = 3.8, \frac{18}{10} = 1.8, \frac{11}{20} = 0.55\)

Draw bars with these heights at midpoints 5.5, 10.5, 20.5, 30.5, and 40.5.