Group numerical data into class intervals

Here are the values of the number of calls answered by staff at a call centre in a shift, for a sample of 38: 1, 21, 22, 93, 5, 23, 25, 48, 2, 98, 94, 76, 96, 81, 83, 67, 21, 57, 67, 99, 44, 27, 29, 13, 23, 87, 17, 82, 91, 32, 61, 56, 20, 60, 45, 77, 62, 43

All listed values are whole numbers. Each interval includes both written endpoints; the next whole number starts the next interval

Use class intervals of width 20, starting at 0: 0–19, 20–39, 40–59, 60–79, 80–99