Question

The mean lifetime of a tire is 48 months with a standard deviation of 7 months. If 147 tires are sampled, what is the probability that the mean of the sample would be greater than 48.83 months? Round your answer to four decimal places.

Answer 1

Solution :

Given that ,

mean = = 48

standard deviation = = 7

n = 147

= 48

= / n = 7/ 147 = 0.5774

P( >48.83 ) = 1 - P( <48.83 )

= 1 - P[( - ) / < (48.83 -48) /0.5774 ]

= 1 - P(z <1.44 )

Using z table

= 1 - 0.9251

= 0.0749

probability= 0.0749