Is it correct to say that in a histogram,the area of each rectangle is proportional to the class size of the corresponding class interval? If not,correct the statement.

The weights (in $kg$) of $11$ students are given below:
$37, 42, 40, 39, 41, 35, 37, 36, 40, 40, 42$
Find the median of the data.

In the class intervals $10-20$ and $20-30$,the number $20$ is included in:

The mean of $3, -3, -3, 3, 3, -3$ is ..........

The facts or figures,which are numerical or otherwise,collected with a definite purpose are called .......

The marks obtained (out of $25$ marks) by $40$ students in an examination are as given below:
$\begin{array}{rrrrrrrrrr} 8, & 12, & 23, & 9, & 5, & 20, & 16, & 3, & 6, & 23 \\ 10, & 6, & 21, & 1, & 18, & 17, & 18, & 16, & 16, & 12, \\ 3, & 15, & 21, & 7, & 12, & 5, & 2, & 7, & 13, & 24, \\ 13, & 18, & 8, & 2, & 20, & 5, & 13, & 7, & 23, & 16 \end{array}$
Represent the data given above by a grouped frequency distribution table,taking the class intervals as $0-5, 5-10, \dots$ etc.