In: Statistics and Probability
An automobile manufacturer has offered a 6 yr / 60,000 mi. power train warranty. If the power train has a life expectancy of 61,000 mi. with a standard deviation of 8,000 mi., what is the probability that the average life of powertrains from 625 randomly selected automobiles will be fewer than 60,497.6 mi.?
The values provided in the question are as below
Mean = = 61000
standard deviation = = 8000
sample size = = 625
We have to find the probability that the average life of powertrains from 625 randomly selected automobiles will be fewer than 60,497.6
------------(1)
We convert this into Z using following way
------------------(2)
Using equation (2) in equation (1) we get
We have to find the probability of Z fewer than -1.57 using the following command in Excel.
The command is =NORMSDIST(Z) then press Enter
here, Z = -1.57
=NORMSDIST(-1.57) then press Enter we get the value probability is 0.0582
The probability that the average life of powertrains from 625 randomly selected automobiles will be fewer than 60,497.6 is 0.0582