When the investigator has personally obtained the information for a particular purpose,this data is called ........ data.

Convert the given frequency distribution into a continuous grouped frequency distribution:

Class interval	Frequency
$150-153$	$7$
$154-157$	$7$
$158-161$	$15$
$162-165$	$10$
$166-169$	$5$
$170-173$	$6$

In which intervals would $153.5$ and $157.5$ be included?

The mean of the $10$ observations is $11$. If one new observation is included,their mean becomes $12$. The included new observation is ........

If the mean of the observations $x, x+3, x+5, x+7, x+10$ is $9,$ find the mean of the last three observations.

For drawing a frequency polygon of a continuous frequency distribution,we plot the points whose ordinates are the frequencies of the respective classes and abscissae are respectively:

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.