The waiting time in milliseconds, W, for accessing one record from a computer database is the continuous uniform (0,10) random variable. The read time R (for moving the information from the disk to main memory) is 3 milliseconds. The random v ariable X milliseconds is the total access time ( waiting time + read time) to get one block of information from the disk. Before Performing a certain task, the computer must access 12 different blocks of information from the disk. ( Access times for different blocks are independent of one another.) The total access time for all the information is a random variable A milliseconds.
(a) What is E[X]?
(b) What is Var[X]?
(c) What is E[A]?
(d) What is σA? time?
(e) Use the central limit theorem to estimate P[A > 116ms].
(f) Use the central limit theorem to estimate P[A < 86ms].