# Scientists Say: Mean, median and mode

## There are multiple ways to describe the central value in a set of numbers Let’s talk about how to calculate mean, median and mode — three different ways to describe the middle number in a dataset. SDI Productions/Getty Images

#### Mean (noun, “MEEN”), Median (noun, “MEE-dee-in”) and Mode (noun, “MOHD”)

Mean, median and mode are three different ways to describe the central value, or measurement, in a set of data. Knowing the central or typical value in a dataset can help reveal trends in the data as well as outliers.

For instance, say you want to know how many pencils a person typically carries in their backpack. So, you ask each of your classmates how many pencils they have in their backpacks. Their answers are: 3, 4, 2, 2, 6, 4, 2, 2 and 5.

The mean is the average of those numbers. To find the average, add all the numbers together and divide by the number of numbers you added. That is, add up 3 + 4 + 2 + 2 + 6 + 4 + 2 + 2 + 5 = 30. Then, divide that by how many numbers you added together, which was nine numbers: 30 ÷ 9 = 3.333. So, the average number of pencils that your classmates have in their backpacks is 3.333.

The median of a dataset is the middle number. You can find it by putting all the numbers in order from smallest to largest. For example: 2, 2, 2, 2, 3, 4, 4, 5, 6. The middle number is three, because it has four numbers on either side of it. (If you have a dataset with an even number of numbers, there is no middle number. But you can still find a median. To do this, find the middle two numbers in the dataset. Then, take the average of those two numbers. That is, add them together and divide the sum by two.)

The mode is simply the most common number in a dataset. In our example, the mode is 2, because it appears four times in the dataset. The number 4 appears only twice. And the numbers 3, 5 and 6 appear only once. Some datasets have more than one mode. And other datasets, where each number appears only once, have no mode at all.

#### In a sentence

One survey found that the median number of texts teens send per day is 30.