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 40: 55, 53, 28, 20, 18, 8, 10, 19, 28, 66, 67, 6, 54, 38, 25, 24, 27, 61, 69, 65, 48, 32, 31, 17, 30, 33, 15, 41, 2, 26, 20, 7, 61, 49, 17, 18, 39, 36, 0, 42

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 10, starting at 0: 0–9, 10–19, 20–29, 30–39, 40–49, 50–59, 60–69