Page 2 - Lesson Note MCT 2 54

− .
Median = + 2 ×
1

50 − 31
= 29.5 + × 10
20
190
= 29.5 +
20

= 29.5 + 9.5 = 39

Calculation of median in open end series

In case of open-end classes, the lower limit of the first-class interval and

upper limit of the last class is not given. Median is said to be the best
average in open-end class interval series.

Ex: - calculate the value of median from the following distribution.

Marks (X) No of students (F)

Below 10 3
10 – 20 13
20 – 30 18
30 – 40 11

40 and above 5

Solution: - calculation of median

Marks (X) No of students (F) Cumulative frequency
(C.F)

Below 10 3 3
10 – 20 13 16
20 – 30 18 34
30 – 40 11 45

40 and above 5 50
= ∑ = 50

Median = ℎ ℎ
2

50
= = 25th data in the series.
2
Median class is 20 - 30

= 20 f =18, c. f = 16, i = 10.
1