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\ 06-Jan-2025 Bharat Arora Proof-6 Reader’s Sign _______________________ Date __________

20-29 |||| |||| ||| 13
30-39 |||| |||| 10

40-49 |||| |||| |||| 14
50-59 |||| || 7

60-69 |||| 4
Total 60

Such a type of distribution is called discontinuous distribution. In this grade, we shall deal with
only continuous frequency distribution.

Example 1: The data showing the heights (in cm) of 50 students of a school are as follows:
139 134 139 140 134 128 129 135 132 126

137 132 132 139 133 136 138 133 139 129
135 140 133 131 136 130 140 138 132 133
137 138 140 130 139 133 136 139 133 131

127 138 132 134 133 130 138 134 131 127
Using tally marks, make a frequency distribution table with suitable class intervals.

Solution: We first observe the minimum and maximum values. In the data shown above, the
minimum and maximum heights are 126 cm and 140 cm, respectively.
\ Range = 140 – 126 = 14
14
.
To organise the data in 5 class intervals, we should take the class size = = 28 ≈ 3
5
So, we should have 5 classes each of size 3. These are, 126–129, 129–132, 132–135, 135–138 and
138–141. Now, we can construct the frequency distribution table as shown below.

Group Frequency Distribution Table
Height (in cm) Tally marks No. of students

(Class Intervals) (Frequency)
Height 129 cm is 126–129 |||| 4
not included here
129 –132 |||| ||| 8
Height 129 cm will 132–135 |||| |||| |||| | 16
be included here 135–138 |||| || 7

138–141 |||| |||| |||| 15
Total 50

Maths Talk
For a given data, you may construct different grouped frequency distributions depending on the
number of groups (in which you are interested) and their widths. What will be changed if you reorganise the
above data in the class intervals 125-130, 130-135, 135-140 and 140-145? Discuss.

93 Data Handling