Find the mean of the first five prime numbers.

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.

Two sections of Class $IX$ having $30$ students each appeared for a mathematics olympiad. The marks obtained by them are shown below:
$\begin{array}{lllllllllllllll}46 & 31 & 74 & 68 & 42 & 54 & 14 & 61 & 83 & 48 & 37 & 26 & 8 & 64 & 57 \\ 93 & 72 & 53 & 59 & 38 & 16 & 88 & 75 & 56 & 46 & 66 & 45 & 61 & 54 & 27 \\ 27 & 44 & 63 & 58 & 43 & 81 & 64 & 67 & 36 & 49 & 50 & 76 & 38 & 47 & 55 \\ 77 & 62 & 53 & 40 & 71 & 60 & 58 & 45 & 42 & 34 & 46 & 40 & 59 & 42 & 29\end{array}$
Construct a grouped frequency distribution table for the data above using the classes $0-9, 10-19$,etc.,and hence find the number of students who secured more than $49$ marks.

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

The ............. of each class of frequency distribution is shown on the $x$-axis,in a frequency polygon.

The scores (out of $100$) obtained by $33$ students in a mathematics test are as follows:
$69, 48, 84, 58, 48, 73, 83, 48, 66, 58, 84$
$66, 64, 71, 64, 66, 69, 66, 83, 66, 69, 71$
$81, 71, 73, 69, 66, 66, 64, 58, 64, 69, 69$
Represent this data in the form of a frequency distribution table.