The following grouped frequency distribution table indicates the marks obtained by students on a Maths test.

(Marks: 20)

Mark (%). Number of Students

0 -< 20 4

20 -< 40 11

40 -< 60 18

60 -< 80 12

80 -< 100 5

n= 50

Calculate the following, using the appropriate formulae: [Note: ALL calculations must be shown. Final answers should be given to two decimal places]

Q.7.1.1 The mean. Interpret the answer

Q.7.1.2 The mode. Interpret the answer.

Q.7.1.3 The third quartile. Interpret the answer.

Q.7.1.4 The 67th Percentile. Interpret the answer.

Q.7.1.5 The standard deviation.