00:01
In this question, we're given the rate of this drive failure in a year is 10%.
00:08
In part a, your data is stored in a hard disk and a copy stored in the second hard disk.
00:13
I'm going to let a denote the event the first hard disk will fail.
00:18
B denote the event the second hard disk will fail.
00:24
Probability of event a, the first hard disk will fail is 10 % or 0 .1 in decimal.
00:29
Probability of event b is also 10 % or 0 .1.
00:36
Both events are independent each other.
00:40
And for independent event, we have this relationship.
00:45
Probability of a intercept b is equals to probability of a times probability of b.
00:54
Take note that n is times set notation is intercept or is plus set notation is union.
01:00
I want to find probability during a year you can avoid disaster with at least one working drive.
01:07
Now i'll take one minus the complement to at least one working drive.
01:11
That will be probability both will fail.
01:18
So both fail means the first disk will fail.
01:21
There's event a.
01:22
N is intersect.
01:27
Second this will fail.
01:28
There's event b.
01:30
So probability a intercept b.
01:34
Since a and b are independent, probability of a and a set b is probability of a times probability of b...