George Smith own's George's Joint, a gas station and convenience store. George is trying to get a better understanding of his business and wants to estimate the mean number of gallons of gasoline sold to his customers. Assume the number of gallons of gasoline sold follows a normal distribution with a population standard deviation of 2.3 gallons. From his records, he randomly selects 60 sales and find the mean number of gallons sold is 8.6. Develop a 99% confidence interval for the population mean. What is the upper boundary? (your answer should be in the format x.xx)

Definition Definition Measure of central tendency that is the average of a given data set. The mean value is evaluated as the quotient of the sum of all observations by the sample size. The mean, in contrast to a median, is affected by extreme values. Very large or very small values can distract the mean from the center of the data. Arithmetic mean: The most common type of mean is the arithmetic mean. It is evaluated using the formula: μ = 1 N ∑ i = 1 N x i Other types of means are the geometric mean, logarithmic mean, and harmonic mean. Geometric mean: The nth root of the product of n observations from a data set is defined as the geometric mean of the set: G = x 1 x 2 ... x n n Logarithmic mean: The difference of the natural logarithms of the two numbers, divided by the difference between the numbers is the logarithmic mean of the two numbers. The logarithmic mean is used particularly in heat transfer and mass transfer. ln x 2 − ln x 1 x 2 − x 1 Harmonic mean: The inverse of the arithmetic mean of the inverses of all the numbers in a data set is the harmonic mean of the data. 1 1 x 1 + 1 x 2 + ...