What is Frequency Curve?

A frequency curve is a result of joining the vertices of a frequency polygon with a smooth curve. It is also referred to as a Smoothed Frequency Curve. The frequency curve may not always go through all of the points of the frequency polygon, but it passes through them as closely as possible.

• A frequency curve should be carefully constructed to avoid sharp edges.
• The curve is drawn freehand in a way that makes the area covered roughly equal to that of the polygon.
• This curve should begin and stop at the baseline. It is usually extended to the middle point of the class interval outside of the histogram.
• The total number of frequencies in the whole distribution should be represented by the area under the curve.

Steps of Frequency Curve 

1. Using the given data, create a histogram. 
2. Determine the midpoints of the upper horizontal side of each rectangle. 
3. To create a frequency curve, join the mid-points of the adjacent rectangles of the histogram using a smooth free hand. 
4. With a free hand, extend the ends of the frequency curve to the baseline.

Example of Frequency Curve: 

Draw a frequency curve from the following distribution.

Solution:

The continuous frequency distribution applies in this case, as there is a frequency distribution with equal class intervals. Firstly, the histogram is prepared, and then the frequency curve. The class interval will be plotted on the X-axis, while the frequency distribution will be plotted on the Y-axis.