00:01
On this problem, we're told that the probability of a diode failure is 0 .02, and a board has 200 diodes, and so in is 200.
00:09
Now, if we treat this like a binomial random variable, this means that the probability of x is 200 choose x times 0 .02 to the x times 0 .98 to the 200 minus x.
00:27
Just using our formulas for the binomial distribution.
00:31
Now in a, we want to find the mean number of failures.
00:34
Well, for a binomial, the mean is equal to n times p, and so this is 0 .02 times 200, which is 4.
00:50
On part b, we want the variance, and the variance for a binomial random variable is n p times 1 minus p, and so this is 200 times 0 .02 times 0 .98, which is 3 .92...