The table below shows height in cm of form 4 students in Westlands Secondary School.

Height(cm) | 150-154 | 155-159 | 160-164 | 165-169 | 170-174 |

Frequency(f) | 18 | 16 | 24 | 28 | 14 |

- Using an assumed mean of 162, calculate;
- mean height
- Standard deviation

- if the heights of each student increases by 5cm. Write down
- The new mean
- The new standard deviation

- Calculate the 30
^{th} percentile