Maths

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 6 11 7 4 4 2 1
States/U.T.
Source : Seventh All India School Education Survey conducted by NCERT
Solution : Let us find the class marks, x i
, of each class, and put them in a column
(see Table 14.6):
Table 14.6
Percentage of female Number of x i
teachers States /U.T. ( f i
)
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 d i
= x i
– 50 and
xi
50
u
i .
10
We now find d i
and u i
and put them in Table 14.7.