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 (cm)

4

10

11

15

16

20

21

25

26

30

Frequency

22

32

78

40

28

(i)

Draw a cumulative frequency graph to illustrate the data.

[4]

(ii)

28% of these daffodils are of height

h

cm or more. Estimate

h

.

[2]

(iii)

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.