In an examination the marks (out of 100) obtained by students are grouped as follows. The mean mark of the distribution is known to be 70.
(a) (i) Find the missing frequency f in the class 60–70.
(b) (ii) After determining f, compute the median and mode of the distribution.
(c) (iii) Which of the three measures—mean, median or mode—would you report to describe the ‘average’ performance of the class? Justify your answer.
(d) Marks (out of 100) | Number of Students
40–50 | 3
50–60 | 9
60–70 | f
70–80 | 15
80–90 | 8
90–100 | 5