The Lesson

We can find the range of a set of numbers presented in a frequency table.

How to Find the Range from a Frequency Table

Finding the range from a frequency table is easy.

Question

The frequency table below shows the test scores for a class of students. What is the range of the test scores?

Step-by-Step:

1

Make sure the entries in the Score column are in numerical order. In our example, the entries are in numerical order.

2

Find the lowest entry in the Score column (with a Frequency greater than 0).

In our example, the lowest entry is 5. The lowest test score is 5.

3

Find the highest entry in the Score column (with a Frequency greater than 0).

In our example, the highest entry is 10. The highest test score is 10.

3

Subtract the lowest number (5) from the highest number (10).
10 − 5 = 5

Answer:

The range of the test scores is 5.

Lesson Slides

The slider below gives another example of finding the range from a frequency table.

Beware

Make Sure the Numbers Are in Order

Make sure the numbers in the left most column are in order.

Don't forget: The whole row, not just that in the first column, needs to be rearranged. Each number in the Frequency column corresponds to the Number to its left.

Careful of 0 Frequencies

What is the range of the frequency table below?

It is tempting to think that it is:
Range = 4 − 1 = 3
However, Number 1 and 4 have a Frequency of 0. That means there is actually no 1 and 4 in the set of numbers. Just ignore any row with a Frequency of 0. The true range is:
Range = 3 − 2 = 1