EXAMPLE 4.27 Tread Life

The actual tread life of a 40,000-mile automobile tire has a Normal probability distribution with miles and miles. We say has an distribution. From a manufacturer's perspective, it would be useful to know the probability that a tire fails to meet the guaranteed wear life of 40,000 miles. Figure 4.14 shows this probability as an area under a Normal density curve. You can find it by software or by standardizing and using Table A. From Table A,

The manufacturer should expect to incur warranty costs for about 3.4% of its tires.