Question

A quality control expert at Glotech computers wants to test their new monitors. The production manager claims they have a mean life of 83 months with a variance of 81. If the claim is true, what is the probability that the mean monitor life would be greater than 81.2 months in a sample of 146 monitors? Round your answer to four decimal places.

Answer 1

Solution :

Given that ,

mean = = 83

^{2 = 81}

standard deviation = = 9

n = 146

= 83

= / n = 9/ 146 = 0.74

P( >81.2 ) = 1 - P( <81.2 )

= 1 - P[( - ) / < (81.2-83) /0.74 ]

= 1 - P(z <-2.43 )

Using z table,    

= 1 - 0.0075

probability= 0.9925