Relative frequencies tell us how often certain events occur, relative to the total number of events.
For example, the following table shows how many items a shop sold in different price ranges in a given week:
| Item Price | Frequency | Relative Frequency |
|---|---|---|
| $1 – $10 | 20 | 0.303 |
| $11 – $20 | 21 | 0.318 |
| $21 – $30 | 13 | 0.197 |
| $31 – $40 | 8 | 0.121 |
| $41 – $50 | 4 | 0.061 |
There were 66 items sold in total. Thus, we found the relative frequency of each class by taking the frequency of each class and dividing by the total items sold.
For example, there were 20 items sold in the price range of $1 – $10. Thus, the relative frequency of the class $1 – $10 is 20 / 66 = 0.303.
Next, there were 21 items sold in the price range of $11 – $20. Thus, the relative frequency of the class $11 – $20 is 21 / 66 = 0.318.
And so on.
The following step-by-step example shows how to calculate relative frequencies on a TI-84 calculator.
Step 1: Enter the Data
First, we will enter the data values.
Press Stat, then press EDIT. Then enter the values in column L1:
Step 2: Calculate the Relative Frequencies
Next, highlight the top of column L2 and type in the following formula:
Here’s how to actually type in this formula:
- Press 2nd, then press 1. This will input “L1” in the formula.
- Press ÷. This will input “/” in the formula.
- Press 2nd, then press STAT. Scroll over to “MATH” and then press 5. This will input “sum(” in the formula.
- Press 2nd, then press 1. This will input “L1” inside the sum() in the formula.
- Press ). This will input the second “)” at the end of the formula.
Once you press Enter, the relative frequencies will appear in column L2:
Here’s how to interpret the output:
- The relative frequency of the first class is .30303.
- The relative frequency of the first class is .31818.
- The relative frequency of the first class is .19697.
- The relative frequency of the first class is .12121.
- The relative frequency of the first class is .06061.
Note that the sum of all of the relative frequencies is 1.
Additional Resources
How to Find a Five Number Summary on a TI-84 Calculator
How to Find Interquartile Range on a TI-84 Calculator
How to Find Sample Variance on a TI-84 Calculator