Standard Deviation: A measure of the dispersion of a set of data from its mean. These are the steps to calculate it by hand. I recommend using a table to keep track of your values; we will practice this below. Step 1: List the values and find the mean (column 1). Step 2: Find the distance between each value and the mean (column 2). Step 3: Find the squares (second power) of all the deviations from the mean (column 3). Step 4: Add all the squares of the deviations from the mean (bottom of column 3). Try this: The daily temperatures (in degrees Fahrenheit) one week in January were 32 36 29 34 31 33 27 34

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 + ...