Use the following frequency distribution (of SAMPLE DATA)in answering the questions

Use the following frequency distribution (of SAMPLE DATA)in answering the questions: class 0-10 f=10; class 10-20 f=20; class 20-30 f=40; class 30-40 f=20; class 40-50 f=10.

QUESTION 2
what is the midpoint of the 3rd class?
5 points 

QUESTION 3
What is the total number of observations in the frequency distributuion?
5 points 

QUESTION 4
What is the relative frequency of the 3rd class?
5 points 

QUESTION 5
In the formula for the standard deviation in this problem do you use "N' or "n-1"?
5 points 

QUESTION 6
what is the value of the mean?
40 points 

QUESTION 7
what is the value of the standard deviation?