Relative frequency is the proportion (percentage) of a sample that belongs to a particular class. We calculate the relative frequency by dividing the class frequency by the total number of data points, n. The sum of the relative frequencies should be one, but due to rounding errors, sometimes it is not exactly one.
Absolute frequency is the number of times a sample belongs to a particular class. The column labeled "Frequency" in the table below represents the absolute frequency.
Table 4. Actual and Relative Frequency of Serum Glucose Levels in 130 Hospital Employees.| Intervals (mg/dL) | Tally | Frequency | Relative Frequency |
| 65–70 | \\ | 2 | 0.015 |
| 70–75 | \\\\ \\ | 7 | 0.054 |
| 75–80 | \\\\\\\\ \ | 16 | 0.123 |
| 80–85 | \\\\\\\\\\\\\\\\\\\\\\\\ \ | 31 | 0.238 |
| 85–90 | \\\\\\\\\\\\\\\\ \\\\ | 24 | 0.185 |
| 90–95 | \\\\\\\\\\\\ \\\ | 18 | 0.138 |
| 95–100 | \\\\\\\\ \\\ | 13 | 0.100 |
| 100–105 | \\\\\\\\ | 10 | 0.077 |
| 105–110 | \\\\ | 5 | 0.038 |
| 110–115 | \\\\ | 4 | 0.031 |
| Total | n=130 | 0.999 |
