Question

Quick Start Company makes 12-volt car batteries. After many years of product testing, the company knows that the average life time(x) of a Quick Start battery is normally distributed with a mean of 45 months and a standard deviation of 8 months. What is the probability that a randomly picked 12-volt car battery that was produced by Quick Start Company has a life time that is less than 36 months?

Answer 1

Solution :

Given that ,

mean = = 45

standard deviation = = 8

P(x < 36 ) = P[(x - ) / < (36 - 45) / 8 ]

= P(z < -1.13)

= 0.1292 , Probability = 0.1292