Question

The life-time in hours of a certain electrical equipment has the normal distribution with mean=80 and standard deviation=16. I. What is the probability that the equipment that the equipment lasts at least 100 hours? II. If the equipment has already lasted 88 hours, what is the conditional probability that it will last at least another 12 hours?

Answer 1

0.89435

Explanation:

Given that :

Mean (m) = 80

standard deviation (s) = 16

P(equipment last at least 100 hours ;

P(x ≥ 100)

USing the relation to obtain the standardized score (Z) :

Z = (x - m) / s

Z = (100 - 80) / 16= 1.25

p(Z < 1.25) = 0.89435 ( Z probability calculator)