Graphic Representation of Data — Ogives (Cumulative Frequency Curves)

A cumulative frequency curve, commonly called an ogive, plots the running (cumulative) total of frequency against the class boundaries of a continuous frequency distribution. Two ogives can be drawn from the same distribution:

• The 'less than' ogive — cumulative frequency (the number of observations up to a class) is plotted against the upper boundary of each class. Since cumulative frequency can only rise or stay the same as we move to higher classes, this ogive is always a rising curve.
• The 'more than' ogive — cumulative frequency (the number of observations at or above a class) is plotted against the lower boundary of each class. This ogive is always a falling curve. …