When dealing with a set of data, such as daily high temperatures, one can determine the center of the data by calculating the mean. Often called the average, this familiar measure is calculated by adding up the individual values and dividing by the number of values. Note that the mean is typically more precise than any single observation.
For this one-month, high temperature dataset from Asheville, NC, the sum of the 31 temperatures is 2045. The mean equals 2045 divided by 31 or approximately 66°F.
2.1.2 Limitations of the Mean Value
There’s one caveat to working with mean values. They can be skewed by the presence (or absence) of just one observation if it is very different from the other values.
For our Asheville dataset, imagine that one of the 62°F temperatures was mistakenly recorded as 262°F. That would change the mean (average) value to approximately 72°F. A 6.45°F difference in the average monthly temperature is a very large change, climatically speaking.