Page 4 - 10-Math-6 BASIC STATISTICS

61. .BQausaicdSratatitcisEtiqcsuations eeLleeaarrnn..Ppuunnjjaabb

(iv) Start writing the classes or groups of the frequency distribution
usually starting from the minimum observation and keeping
in view the size of a class.
(v) Record the observations from the data by using tally marks.
(vi) Count the number of tally marks and record them in the
frequency column for each class.

Example 2: The following are the marks obtained by 40 students in
mathematics of class X.
Make a frequency distribution with a class interval of size 10.
51, 55, 32, 41, 22, 30, 35, 53, 30, 60, 59, 15, 7, 18, 40, 49, 40, 25, 14,
18,19, 2, 43, 22, 39, 26, 34, 19, 10, 17, 47, 38, 13, 30, 34, 54, 10, 21,
51, 52.

Solution: Let X = marks of a student.
From the above data we have Xmin = 2, Xmax = 60. It is given that h = 10.
We can either start from 2 or the nearest smallest integer 0 for our

convenience. There are two ways to make frequency distribution.

(a) We may write the actual observations falling in the

respective groups. This is given as follows:

Classes/Groups Observations Frequency

0 _____ 9 2, 7 2

10 _____19 10, 10, 13, 14, 15, 17, 18, 18, 19, 19 10

20 _____ 29 21, 22, 22, 25, 26 5

30_____ 39 30, 30, 30, 32, 34, 34, 35, 38, 39 9

40 _____ 49 40, 40, 41, 43, 47, 49 6

50_____ 59 51, 51, 52, 53, 54, 55, 59 7

60 ______ 69 60 1

(b) Use tally marks for recording each observation in the
respective group. This is given in the following table:

4