Question: The US compiles enrollment data on public schools and reports the info. The following frequency distribution for the enrollment by grade level for a given year. Frequencies are in thousands.

Grade Frequency

x f

9 3604

10 3131

11 2749

12 2488

Total

a. determine probability distribution of the random variable x (and find rel. frequencies)

b. Construct probability histogram for the random variable x.

c. What is the probability that a randomly selected student is in either 9 th or 10 th grade?

d. What is the probability that randomly selected student is in at most 11 th grade?

e. Find the mean and standard deviation of the random variable x.