Question

Class mark	12.5	17.5	22.5	27.5	32.5	37.5	42.5
Frequency	12	17	22	27	30	21	16

1. From the distribution, given above, construct a frequency table.
2. Use the table obtained in part (a) to draw : (i) a histogram, (ii) an ogive.

Answer 1

(a) Difference in consecutive class marks = 17.5 − 12.5 = 5

First class interval will be 10 – 15 and so on. 

Class Mark	Class Interval	Frequency	c.f.
12.5	10 – 15	12	12
17.5	15 – 20	17	29
22.5	20 – 25	22	51
27.5	25 – 30	27	78
32.5	30 – 35	30	108
37.5	35 – 40	21	129
42.5	40 – 45	16	145

Total = 145

  
(b) Now plot the points (15, 12), (20, 29), (25, 51), (30, 78), (35, 108), (40, 129), (45, 145) and join them to obtain an ogive.