Renáta Németh, Dávid Simon

ELTE

Appropriate for **interval-ratio** variables

The above data again:

The frequency polygon shows the differences in frequencies or percentages among classes of the categories of an interval-ratio variable. Points representing the frequencies of each class are placed above the midpoint of the class and are joined by a straight line.

It is similar to the histogram; differences:

**fix width**of intervalspercentages (or frequencies) are assigned to the

**midpoint**of the interval

*Example:* In a reaction time trial time is the variable measured, which is interval-ratio. Frequency distribution of a classification is shown in the table below:

More easily readable when presented graphically (width is fixed at 5, the first and the last class is defined as 20-25 and 55-60, respectively):