Question

The time until failure of an electronic device has an exponential distribution with mean 15 months. If a random sample of five such devices are tested, what is the probability that the first failure among the five devices occurs a after 9 months? b before 12 months?

Answer 1

The probability that the first failure occurs among the five devices is given by

(a) 9 months =
`(9)/(15) or =0.6`

(b) 12 months=
`(12)/(15) or = 0.8`

Explanation:

probability is given as the; number of required outcome/ total number of possible outcome.