Define: class-interval.

Define: lower class-limit and upper class-limit.

Define: class-boundary, lower and upper class-boundaries

Define: class-length.

What do you mean by class-frequency? What is relative class-frequency of any class-interval?

What is frequency density of a class-interval? If the class-frequency of the class $19.5-29.5$ be $7$, then what is its frequency density?

The number of babies of each of $50$ families of your locality are given below:

$\begin{array}{ccc}4& & 0\\ 1& & 0\\ 5& & 4\\ 6& & 2\\ 2& & 2\end{array}\begin{array}{cccc}& 1& & 2\\ & 2& & 2\\ & 1& & 1\\ & 2& & 3\\ & 4& & 2\end{array}\begin{array}{cccccc}& 6& & 4& & 2\\ & 4& & 2& & 2\\ & 2& & 2& & 1\\ & 3& & 4& & 1\\ & 2& & 3& & 6\end{array}\begin{array}{cccccc}& 3& & 5& & 4\\ & 4& & 2& & 3\\ & 4& & 3& & 5\\ & 1& & 2& & 1\\ & 1& & 4& & 6\end{array}$

Prepare a grouped frequency distribution of the above raw data taking the class-intervals $0-2, 2-4, 4-6,.......$etc.

The marks obtained by $20$ students of class $-\mathrm{IX}$ of Sanskrit (full marks $-50$) are given below:

$\begin{array}{c}48\\ 46\end{array}\begin{array}{cccccc}& 48& & 49& & 49\\ & 48& & 49& & 49\end{array}\begin{array}{cccccc}& 48& & 40& & 45\\ & 49& & 48& & 44\end{array}\begin{array}{cccccc}& 44& & 49& & 44\\ & 48& & 49& & 49\end{array}$

Prepare a grouped frequency distribution of the above raw data taking the class-intervals $40-45, 45-50,......$etc. using tally-marks.

The electric bills (in $₹$) of $45$ houses of Bamangachi collected by Runu, Jhunu and Lalita are given below

$\begin{array}{ccc}116& & 127\\ 75& & 92\\ 95& & 108\\ 118& & 61\\ 92& & 75\end{array}\begin{array}{cccc}& 100& & 82\\ & 129& & 78\\ & 115& & 121\\ & 129& & 127\\ & 98& & 65\end{array}\begin{array}{cccccc}& 80& & 101& & 91\\ & 87& & 101& & 65\\ & 128& & 63& & 76\\ & 91& & 130& & 125\\ & 110& & & & \end{array}\begin{array}{cccccc}& 65& & 95& & 89\\ & 52& & 59& & 65\\ & 130& & 116& & 108\\ & 101& & 116& & 105\\ & & & & & \end{array}$

Prepare a grouped frequency distribution of the above data, the class-length of each of which is $10$.