Question

A quality control expert at Glotech computers wants to test their new laptop monitors. The production manager claims the monitors have a mean life of 89 months with a population standard deviation of 5 months. If the claim is true, what is the probability that the mean monitor life would be greater than 87.8 months in a sample of 123 monitors? Round your answer to four decimal places.

A. 0.5948

B. 0.0001

C. 0.9961

D. 0.5000

E. 0.0039

Answer 1

Solution :

Given that ,

mean = = 89

standard deviation = = 5

= / n = 5/ 123 = 0.4508

P( > 87.8) = 1 - P( < 87.8)

= 1 - P[( - ) / < (87.8 - 89) / 0.4508]

= 1 - P(z < -2.66)

= 1 - 0.0039

= 0.9961

Probability = 0.9961