An ogive graph is a smooth S-shaped curve that is used in statistics. The graph is obtained by plotting the values of cumulative frequency against the upper boundary points of the class intervals.
Cumulative frequency values are obtained by adding successive frequencies of each class interval. The first frequency remains unchanged. The last value in the cumulative frequency column should be the same as the total of all the frequencies.
When plotting the ogive, the upper boundary points must be marked on the X-axis, while the cumulative frequency values must be marked on the Y-axis. The curve is obtained by joining all the plotted values with a pencil without using a ruler. This gives the graph its smooth, S-shaped curve.