To choose an interval, one should always first find the range i.e. highest and the lowest value difference.
Here, from the data set : 95 103 110 86 72 77 97 118 83 101 105 79 78 95 93
The highest number is 118 and the smallest number is 72, and the difference between the two is (118 - 72) = 46
And, divide 46 by 5, we get, 9.2 which is approx = 9.
Now, the lower class boundary will be starting with 72, then, 72 + 9 = 81, then, 81+ 9 = 90. and so on.
Similarly, the upper-class boundary will be one less than the second lowest boundary. i.e. 81-1 = 80, then, 90-1 = 89, and so on.
LCB UCB
72 80
81 89
90 98
99 107
108 116
117 125
126 134
