There are several ways to find the mean, median, mode, and range of a data set. 

To find the mean:

Step 1:  Add all of the numbers in the data set. 

79 + 84 + 98 + 92 + 84 + 88 + 72 + 95 + 91 = 783

Step 2:  Divide the sum of the numbers in the data set by the number of addends. 

783 $÷$9 = 87 

The mean is 87. 

To find the median:

Step 1: Put the numbers in order from least to greatest. 

72, 79, 84, 84, 88, 91, 92, 95, 98

Step 2:  Find the middle number in the data set. 

72, 79, 84, 84, 88, 91, 92, 95, 98 

The median is 88. 

To find the mode:

Find the number that occurs the most often: 

72, 79, 84, 84, 88, 91, 92, 95, 98 

The mode is 84. 

To find the range:

Subtract the smallest number from the greatest number in the data set: 

98 − 72 = 26 

The range is 26. 

Finding the mean, median, and mode is also called finding the central tendency. Range is also called variability.

Activity 1

Students often have trouble finding the median if there is an even number of data. Sometimes students forget that there can be more than one mode. While your student is working on her homework, remind her: 

1. How to Solve Problems with an Even Number of Data

The median is the average of the middle two numbers in a data set. 

For example, find the median of 7, 10, 11, 13, 13, and 13. 

The middle two numbers are 11 and 13.

11 + 13 = 24

24 $÷$ 2 = 12

The median is 12. 

2. Some Data Sets Have More Than One Mode

For example, find the mode of 84, 99, 99, 121, 124, and 124. 

The numbers 99 and 124 both occur twice, so both numbers are modes.

Activity 2

Make sure your student understands the definitions of mean, median, mode, and range before he takes a quiz or test in class. Write the following words on the fronts of index cards and their definitions on the backs of the cards. Quiz your student by showing him the front of an index card and having him say the definition for the word. 

mean– the sum of all the numbers in a data set divided by the total number of addends 

median– the middle number when a data set is arranged from least to greatest 

mode– the number that occurs the most often in a data set 

range– the difference between the greatest and least value in a data set 

Once your student knows the definition of each word, make sure he knows how to find the mean, median, mode, and range for the following data sets: