6 On a certain day in spring, the heights of 200 daffodils are measured, correct to the nearest centimetre. The frequency distribution is given below.
| Height \(( \mathrm { cm } )\) | \(4 - 10\) | \(11 - 15\) | \(16 - 20\) | \(21 - 25\) | \(26 - 30\) |
| Frequency | 22 | 32 | 78 | 40 | 28 |
- Draw a cumulative frequency graph to illustrate the data.
- \(28 \%\) of these daffodils are of height \(h \mathrm {~cm}\) or more. Estimate \(h\).
- You are given that the estimate of the mean height of these daffodils, calculated from the table, is 18.39 cm . Calculate an estimate of the standard deviation of the heights of these daffodils.