d.
For numbers 9-12, refer to the probability distribution of the number of books
borrowed from a school library in a day and its corresponding probabilities.
20
25
30
35
40
45
0.1
0.1
0.4
0.2
0.1
0.1
x
P(x)
a. 25
9. What is the mean of the probability distribution?
b. 29
c. 30
d. 32
10. How would you interpret the mean value that you get from item number 8?
a. It is the least number of books borrowed from the school library in a day.
b. It is the largest number of books borrowed from the school library in a day.
c. It is the average number of books borrowed from the school library in a day.
d. It is the difference between the largest and the least number of books
borrowed from the school library in a day.
11. What is the variance of the probability distribution?
a. 38
b. 40
d. 46
c. 43
12. What is the standard deviation of the probability distribution?
a. 6.16
b. 6.32
c. 6.56
d. 6.78​