Observations of a data are $28, 16, 9, 17, 82, 71, 41, 18, 25, 15$. Find the range of the data.

The heights (in $cm$) of $12$ students are as follows:
$159, 148, 138, 150, 165, 166, 145, 152, 155, 160, 147, 151$
Find the mean,the median,and the mode.

Find the median of the observations $18, 8, 12, 3, 20, 4, 10, 5$.

The median of the data $78, 56, 22, 34, 45, 54, 39, 54, 84$ is

The following table shows a frequency distribution for the speed of cars passing through a particular spot on a highway:

Class interval $(km/h)$	Frequency
$30-40$	$3$
$40-50$	$6$
$50-60$	$25$
$60-70$	$65$
$70-80$	$50$
$80-90$	$28$
$90-100$	$14$

Draw the frequency polygon representing the above data without drawing the histogram.

If the information gathered by an investigator is from an already existing source of data,then such information is called .........