, , , , , , , ,
The class width can be found by finding the difference of the maximum data value and the minimum data value (range of data) divided by the number of classes.
The number of classes can be estimated using the rounded output of Sturges' rule, , where is the number of classes and is the number of items in the data set.
Select classes for this example.
Find the data range by subtracting the minimum data value from the maximum data value. In this case, the data range is .
Find the class width by dividing the data range by the desired number of groups. In this case, .
Round up to the nearest whole number. This will be the size of each group.