The observations $7, 15, x-1, x+1, 24, 28$ have been arranged in ascending order. If the median of the data is $21$,find the value of $x$.

The frequency distribution is given below:

Marks	$0-20$	$20-40$	$40-60$	$60-100$
Number of Students	$10$	$15$	$20$	$25$

This distribution has been represented graphically as shown in the image. Is this representation correct? Explain.

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

Classifying the observations $0, 3, 2, 5, 7, 8, 10, 12, 5, 6, 6, 4, 14, 18, 20$ of a data,the frequency of class $0-5$ is ........

The class mark of the class $70-90$ is ...........

The mean of the data: $2, 8, 6, 5, 4, 5, 6, 3, 6, 4, 9, 1, 5, 6, 5$ is given to be $5$. Based on this information,is it correct to say that the mean of the data: $10, 12, 10, 2, 18, 8, 12, 6, 12, 10, 8, 10, 12, 16, 4$ is $10$? Give reason.