Bush cell phone shop is specialized in cell phone sales and repairs. Mr. Bush conduct the annual inventory of its cell phone repairs at the end of the store’s first years. Let assume that the repair cost is normally distributed with a mean of $15.20 and a standard deviation of $7. If a random sample of 40 customers is selected, what is the probability that the mean repair cost of these customers will be more than $16.00 If a random sample of 100 customers is selected, what is the probability that the mean repair cost of these customers will be between $15.10 and $15.90 If a random sample of 50 customers is selected, what is the probability that these customers' mean repair cost will be $14 or less?

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 + ...