Find the range: highest value minus lowest value
Decide the number of classes
Divide the range by the number of classes
Round up to a convenient whole number
Use the result as the class width
Verify that all data values fit into the class intervals
Find the range: highest value minus lowest value
Decide the number of classes
Divide the range by the number of classes
Round up to a convenient whole number
Use the result as the class width
Verify that all data values fit into the class intervals