The following table shows the marks scored by 80 students in an examination: Marks Less than 5 Less than 10 Less than 15 Less than 20 Less than 25 Less than 30 Less than 35 Less than 40 Number of eggs 3 10 25 49 65 73 78 80 Calculate the mean marks correct to 2 decimal places.

Question

Philoid · Accepted Answer

We will find the mean marks using step - deviation method, where A = Assumed mean and h = length of class interval.

Here, let A = 17.5 and h = 5

Since, the class intervals are less - than type, we’ll first convert it into exclusive type.

WEIGHT(G)	MID - POINT(x_i)	DEVIATION(d_i) d_i = x_i – 17.5	NUMBER OF EGGS(f_i)	u_i = d_i/h	f_iu_i
0 - 5	2.5	- 15	3	- 3	- 9
5 - 10	7.5	- 10	7	- 2	- 14
10 - 15	12.5	- 5	15	- 1	- 15
15 - 20	17.5 = A	0	24	0	0
20 - 25	22.5	5	16	1	16
25 - 30	27.5	10	8	2	16
30 - 35	32.5	15	5	3	15
35 - 40	37.5	20	2	4	8
TOTAL			80		17

We have got

A = 17.5, h = 5, Σf_i = 80 & Σf_iu_i = 17

∵ mean is given by

⇒

Thus, mean marks correct to 2 decimal places are 18.56.

Marks	Less than 5	Less than 10	Less than 15	Less than 20	Less than 25	Less than 30	Less than 35	Less than 40
Number of eggs	3	10	25	49	65	73	78	80

The following table shows the marks scored by 80 students in an examination:MarksLess than 5Less than 10Less than 15Less than 20Less than 25Less than 30Less than 35Less than 40Number of eggs310254965737880Calculate the mean marks correct to 2 decimal places.

The following table shows the marks scored by 80 students in an examination:

Marks

Less than 5

Less than 10

Less than 15

Less than 20

Less than 25

Less than 30

Less than 35

Less than 40

Number of eggs

3

10

25

49

65

73

78

80

Calculate the mean marks correct to 2 decimal places.