The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 60000 miles and a standard deviation of 1400 miles. What is the probability that the average life of 4 tires is greater than 58,600 miles?

Features Features Normal distribution is characterized by two parameters, mean (µ) and standard deviation (σ). When graphed, the mean represents the center of the bell curve and the graph is perfectly symmetric about the center. The mean, median, and mode are all equal for a normal distribution. The standard deviation measures the data's spread from the center. The higher the standard deviation, the more the data is spread out and the flatter the bell curve looks. Variance is another commonly used measure of the spread of the distribution and is equal to the square of the standard deviation.