Find the Percentage Frequency

The number of classes can be estimated using the rounded output of Sturges' rule, ${\displaystyle N=1+3.322\log \left(n\right)}$, where ${\displaystyle N}$ is the number of classes and ${\displaystyle n}$ is the number of items in the data set.

Select ${\displaystyle 4}$ 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 ${\displaystyle 9-0=9}$.

Find the class width by dividing the data range by the desired number of groups. In this case, ${\displaystyle \frac{9}{4}=2.25}$.

Round ${\displaystyle 2.25}$ up to the nearest whole number. This will be the size of each group.

Start with ${\displaystyle 0}$ and create ${\displaystyle 4}$ groups of size ${\displaystyle 3}$.

Determine the class boundaries by subtracting ${\displaystyle 0.5}$ from the lower class limit and by adding ${\displaystyle 0.5}$ to the upper class limit.

Draw a tally mark next to each class for each value that is contained within that class.

Count the tally marks to determine the frequency of each class.

The relative frequency of a data class is the percentage of data elements in that class. The relative frequency can be calculated using the formula ${\displaystyle f_i=\frac{f}{n}}$, where ${\displaystyle f}$ is the absolute frequency and ${\displaystyle n}$ is the sum of all frequencies.

${\displaystyle n}$ is the sum of all frequencies. In this case, ${\displaystyle n=3+2+3+1=9}$.

The relative frequency can be calculated using the formula ${\displaystyle f_i=\frac{f}{n}}$.

Simplify the relative frequency column.

Multiply every relative frequency by ${\displaystyle 100}$ to get the percentage frequency.