# What is the definition of a mean?

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A mean is one of three types of measures of central tendency, also known as averages. The mean of a set of numbers is the arithmetic average, calculated by adding together the values in a set of data and dividing the sum by the number of values.

A measure of central tendency is a single value that is meant to identify the central point within a set of data. The mean is the best known and most used of the three types of averages, but it isn't always the most indicative of the central position. The mean can be misleading when there are data points that are outliers. For example, when calculating the mean salary for a group of people, one or two unusually high salaries will affect the mean disproportionately.

The median is a better measure of central tendency when there are outliers as in the salary example, or when the data is skewed (not a normal bell curve). The median is the central value in the data set, such that an equal number of values come before and after it.

The third measure of central tendency is the mode, which is the most frequently occurring value. It is used when one wants to know where a distribution peaks.

The mean is the same as an average. An average is calculated by finding the sum off all the numbers within a set of numbers. This total is then divided by the number of items that were added. Below, I have provided some example questions involving means and their answers:

1. What is the mean (average) of these three numbers: 6, 7, 9?

5 + 4 + 9 = 18

18 / 3 = 6

2. What is the mean (average) weight of the following chimpanzees?

Chimpanzee number one: 80 pounds

Chimpanzee number two: 70 pounds

Chimpanzee number three: 40 pounds

Chimpanzee number four: 80 pounds

Chimpanzee number five : 60 pounds

Chimpanzee number six: 70 pounds

80 + 70 + 40 + 80 + 60 + 70 = 300 pounds

300 pounds / 6 = 50 pounds

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