Question

Assume that there is a 6​% rate of disk drive failure in a year. a. If all your computer data is stored on a hard disk drive with a copy stored on a second hard disk​ drive, what is the probability that during a​ year, you can avoid catastrophe with at least one working​ drive? b. If copies of all your computer data are stored on three three independent hard disk​ drives, what is the probability that during a​ year, you can avoid catastrophe with at least one working​ drive?

Answer 1

The easiest way to do this is calculate the probability that all drives crash, and subtract that from one. The first one is .06 squared subtracted from 1, so it’s .9964 or 99.64%. The second one is .06 cubed subtracted from 1, so it’s .9998, or 99.98 %