NCERT Class 10 Mathematics

STATISTICS 267

Example 2 : The table below gives the percentage distribution of female teachers in
the primary schools of rural areas of various states and union territories (U.T.) of
India. Find the mean percentage of female teachers by all the three methods discussed
in this section.

Percentage of 15 - 25 25 - 35 35 - 45 45 - 55 55 - 65 65 - 75 75 - 85

female teachers

Number of 61174421

States/U.T.

Source : Seventh All India School Education Survey conducted by NCERT

Solution : Let us find the class marks, xi, of each class, and put them in a column
(see Table 14.6):

Table 14.6

Percentage of female Number of xi

teachers States /U.T. (fi)

15 - 25 6 20

25 - 35 11 30

35 - 45 7 40

45 - 55 4 50

55 - 65 4 60

65 - 75 2 70

75 - 85 1 80

Here we take a = 50, h = 10, then di = xi – 50 and

50

10

i

i

u x

.

We now find diand ui and put them in Table 14.7.