Question

Suppose that 50 identical batteries are being tested. After 8 hours of continuous use, assume that a given battery is still operating with a probability of 0.70 and has failed with a probability of 0.30. What is the probability that between 25 and 30 batteries (inclusive) will last at least 8 hours

Answer 1

Binomial Problem with n = 50 and P(op) = 0.0.7

P(31<=50) = 1 - P(0<=x<=30) = 1 - binomcdf(50,0.7,30) = 1-0.0848 = 0.9152