The factory installed brake linings for a certain kind of car have a mean lifetime of 60,000 miles with a 6,000 mile standard deviation. A sample of 100 cars has been selected for testing. What is the standard error of ? (Assume that the finite population correction may be ignored.) The factory installed brake linings for a certain kind of car have a mean lifetime of 60,000 miles with a 6,000 mile standard deviation. A sample of 100 cars has been selected for testing. What is the standard error of ? (Assume that the finite population correction may be ignored.)