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Mean Median and Mode

At some point in math class, you are going to hear the terms: mean, median, and mode. In a given set of numbers:

  • Mean refers to the average of all the numbers.

  • Median refers to the number in the middle.

  • Mode refers to the number most frequently presented in the number set.

To find the mean: Add up all the numbers in the number set and divide by the total number of numbers. For example: In the number set below:

1, 3, 5, 7, 9, 9, 11, 13, 15

Add all the numbers. Your total is: 73

Divide 73 by 9—the total numbers in the set.

The mean of this data set is: 8.111111111 repeating.

The median is easy to find. Since there are 9 numbers in the set, the 5th number is the middle. The first 9 in the set is the median, because four numbers: 1, 3, 5 and 7 are on the first side and 9, 11, 13, and 15 are on the other. If there is an even number of numbers in the set, find the two numbers in the middle, add them, and divide by 2.

The mode is also very easy to find. Simply find the number most frequently presented in the number set. In this case, since there are two 9's, 9 is also the mode. If more than one number is presented in the number set more than one time, it is also the mode.

2, 4, 4, 6, 6, 8, 8, 8

There are 8 numbers in this number set. Add them all together and divide by 8 to get the mean. Since the total of the numbers is 46, the mean is: 5.75

The median numbers are 6 and 6, leaving three on each side of the number set. 6 + 6 = 12. 12 divided by 2 = 6, so the median in this case is still 6.

There are three modes in this number set, because three numbers are repeated more than once. The modes in this number set are: 4, 6, and 8.

6, 9, 12

In this number set, the mean is 9. The total is 27, so we divide 27 by 3 to get the mean.

The median is also 9, because it's the number in the middle.

There is no mode, because each number is presented once in the data set. Whenever you do not see a number repeated in a dataset, there is not a mode.

In many cases, you'll find the mean and median as the same number. This math concept is very easy to master and easy to remember once you get the hang of it.