(solution) The waiting time W for accessing one record from a computer database is a random variable…

(solution) The waiting time W for accessing one record from a computer database is a random variable…

The waiting time W for accessing one record from a computer database is a random variable uniformly distributed between 0 and 10 milliseconds. The read time R (for moving the information from the disk to main memory) is 3 milliseconds. The random variable 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], the expected value of the access time? (b) What is Var[X], the variance of the access time? (c) What is E[A], the expected value of the total access time? (d) What is σA, the standard deviation of the total access time? (e) Use the central limit theorem to estimate P[A > 116ms], the probability that the total access time exceeds 116 ms. (f) Use the central limit theorem to estimate P[A