Mode of the data $15, 14, 19, 20, 14, 15, 16, 14, 15, 18, 14, 19, 15, 17, 15$ is

The marks obtained (out of $100$) by a class of $80$ students are given below:

Marks	Number of students
$10-20$	$6$
$20-30$	$17$
$30-50$	$15$
$50-70$	$16$
$70-100$	$26$

Construct a histogram to represent the data above.

The mean of $25$ observations is $36$. If the mean of the first $13$ observations is $32$ and the mean of the last $13$ observations is $40$,find the $13^{\text{th}}$ observation.

Prepare a continuous grouped frequency distribution from the following data:

Mid-point	Frequency
$5$	$4$
$15$	$8$
$25$	$13$
$35$	$12$
$45$	$6$

Also,find the size of the class intervals.

The width of the class $50.5-55.5$ is .............

After arranging the observations in ascending or descending order,the observation which is obtained in the middle is called .............. of the data.